Orthopaedic Knowledge

Osteomyelitis of Long Bones

2009-10-12T03:10:00.000-07:00

Osteomyelitis is defined as infection in bone. Osteomyelitis in long bones includes infections that differ from one another with regard to duration, etiology, pathogenesis, extent of bone involvement, and type of patient (which can be an infant, child, adult, or compromised or uncompromised host).

Etiology
In hematogenous osteomyelitis, a single pathogenic organism is almost always recovered from the bone. In infants, Staphylococcus aureus, Streptococcus agalactiae, and Escherichia coli are most frequently isolated from blood or bone.

However, in children over one year of age, Staphylococcus aureus, Streptococcus pyogenes, and Haemophilus influenzae are most commonly isolated. The incidence of Haemophilus influenza infection decreases after the age of four years.

In adults, Staphylococcus aureus is the most common organism isolated. Multiple organisms are usually isolated from bone infected as a result of direct inoculation or contiguous focus infection. Staphylococcus aureus remains the most commonly isolated pathogen. However, gram-negative bacilli and anaerobic organisms are also frequently isolated.

Pathogenesis

1. Source of Infection

Osteomyelitis can be caused by hematogenous spread, direct inoculation of microorganisms into bone, or a contiguous focus of infection. Hematogenous osteomyelitis usually involves the metaphysis of long bones in children because long bones of children have very active metabolic rates. The most common causes of direct-inoculation osteomyelitis are penetrating injuries and surgical contamination. Contiguous osteomyelitis commonly occurs in patients with severe vascular disease.

2. Host Factors

Host factors are primarily involved in the containment of the infection once it has been introduced adjacent to or into the bone. Host factors may predispose individuals to the development of osteomyelitis. Host deficiencies that lead to bacteremia favor the development of hematogenous osteomyelitis.

Host deficiencies that are involved in the direct inoculation of organisms and/or contiguous spread of infection from an adjacent area of soft-tissue infection are primarily involved in the lack of containment of the initial infection.

Some patients have an unusual susceptibility to acute skeletal infections when they have sickle cell anemia, chronic granulomatous disease, or diabetes mellitus. Many systemic and local factors influence the ability of the host to elicit an effective response to infection and treatment

Pathology

1. Acute Osteomyelitis

Acute osteomyelitis presents as inflammation accompanied by edema, vascular congestion, and small-vessel thrombosis. In early acute disease, the vascular supply to the bone is decreased by infection extending into the surrounding soft tissue. When both the medullary and the periosteal blood supplies are compromised, large areas of dead bone (sequestra) may be formed in chronic phase.

However, if treated promptly and aggressively with antibiotics and possibly with surgery, acute osteomyelitis can be arrested before dead bone presents.

2. Chronic Osteomyelitis

Pathologic features of chronic osteomyelitis are the presence of necrotic bone (sequestrum), the formation of new bone (involucrum), and the exudation of polymorphonuclear leukocytes joined by large numbers of lymphocytes, histiocytes, and occasionally plasma cells.

New bone forms from the surviving fragments of periosteum and endosteum in the region of the infection. It forms an encasing sheath of live bone, known as an involucrum, surrounding the dead bone under the periosteum.

The involucrum is irregular and is often perforated by openings through which pus may track into the surrounding soft tissues and eventually drain to the skin surfaces, forming a chronic sinus. The involucrum may gradually increase in density and thickness to form part or all of a new diaphysis.

New bone increases in amount and density for weeks or months, according to the size of the bone and the extent and duration of the infection. Endosteal new bone may proliferate and obstruct the medullary canal. After host defense or operative removal of the sequestrum, the remaining cavity may fill with new bone, especially in children. However, in adults, the cavity may persist or the space may be filled with fibrous tissue, which may connect with the skin surface by means of a sinus tract.

Views of the left wrist show a lobulated osteolytic lesion with well-defined borders and surrounding sclerosis in the distal radius. There were minimal expansion, mild periosteal reaction and soft tissue swelling.

The red box encircles the sequestrum at lower part of tibia, the piece of necrotic tissue of tibial bone, that has become separated from the tibia

Signs and Symptoms

Children with hematogenous osteomyelitis may present with acute signs of infection including fever, irritability, lethargy, and local signs of inflammation. Children with hematogenous osteomyelitis usually have noninfected soft tissue enveloping the infected bone and are capable of mounting an effective response to the infection. The joint is usually spared from infection unless the metaphysis is intracapsular, as is found in the proximal part of the radius, humerus, or femur.

Adults with primary or recurrent hematogenous osteomyelitis usually present with vague symptoms consisting of nonspecific pain and low-grade fever of one to three months’ duration. However, acute clinical presentations with fever, chills, swelling, and erythema over the involved bone or bones are occasionally seen.

The source of bacteremia may be a trivial skin infection or a more serious infection such as acute or subacute bacterial endocarditis. Hematogenous osteomyelitis that involves either long bones or vertebrae is an important complication of injection drug abuse. Patients with contiguous osteomyelitis often present with localized bone and joint pain, erythema, swelling, and drainage around the area of trauma, surgery, or wound infection.

Signs of bacteremia such as fever, chills, and night sweats may be present in the acute phase of osteomyelitis but are not seen in the chronic phase. Both hematogenous and contiguous focus osteomyelitis can progress to a chronic condition. Local bone loss, sequestrum formation, and bone sclerosis are common. Persistent drainage and/or sinus tracts are often found adjacent to the area of infection. The patient usually presents with chronic pain and drainage. If fever is present, it is low grade.

External Fixation

2009-10-12T03:04:00.001-07:00

Case summary

36 y/o, Malay gentleman

Patient drove car with around 60km/h and was crashed with lorry from front. He was loss of consciousness and was sent to emergency department by ambulance. Multiple fractures and bleeding were noted. There was an open fracture of right leg, grade 3C in Gustillo classification. X-ray of the right leg was done.

Plain x-ray of the right leg.

This is an anterior-posterior view of distal 1/3 of right knee and proximal 2/3 of right leg. The x-ray showed that there is segmented fracture of tibial plateau, both condyles are split and the tibial shaft is wedged between them, there is intraarticular extended and was type 5 in Schatzker classification. There is no shortening, angulation or rotation of the bone was seen in this view.

This is a lateral view of distal 1/3 of right knee and proximal 2/3 of right leg. The x-ray showed that there is segmented fracture of tibial plateau, There is 10 degree angulation of the tibial bone.There is no shortening or rotation of the bone was seen in this view.

External fixation was done.

This is an anterior-posterior view of distal 1/3 of right knee and proximal 2/3 of right leg. The x-ray showed that there is a interfragmentary screw fixing the fragmented tibial bone. Two pins were passed though th femur bone and another two pins were passed through the tibial bone. There is no angulation, shortening or rotation seen in this view.

This is a lateral view of distal 1/3 of right knee and proximal 2/3 of right leg. The x-ray showed that there is an interfragmentary screw on the fragments. there is no angulation, shortening and rotation of the bone was seen in this view.

External fixation is a surgical treatment which is held by transfixing screws, pins or tensioned wires which are pass through the bone above and below of the fracture site. These are then connected to an external frame or rigid bar. While reducing the fracture in all three planes, hold it in the proper alignment (adjustment of the angulation), it also allow some degree of rigidity and stability. besides it also allow adjustment of length of the bone. External fixation is commonly apply to fracture of long bones (esp. femur, tibia and humerus) and pelvic, but it can also be used for fractures of almost any part of the skeleton (example bone of the hand). Insertion of wires and half pins must be with care, by the knowledge of 'safe corridors' is to avoid nerves or vessels injury.

Indications of external fixation include:

1. Fracture associated with severe soft tissue damage.

external fixation was apply, two pins on the femur bone and two pins on the tibia bone. there are two wounds on the anterior aspect of upper half leg. The wound is measuring 5x3cm and 5x4cm. There is bleeding, no slough, granulation tissue present, slope well-defined edge. There is no maculous pin-site infection.

2. Fracture associated with nerve and vessel damage.
3. Severely comminuted and unstable fracture
4. Non-union where dead or sclerotic fracture fragment can be excised and fragments brought together by fixator
5. Fracture of pelvic which cannot be held by other method
6. Infected fracture
7. Severe multiple injuries

Complications

1. Damage to soft tissue structures.
Surgeon must familiar with the anatomy and the 'safe corridor' to prevent injured to the nerves and vessels.

2. Overdistraction.
Fragments of the bone must come to contact for union to be occur. If there is no contact between of the fragments, union may be delayed or prevented.

3. Pin-track infection.
This is rare but is the most complicated. Therefore, meticulous pin-site care is essential. If infection is occur, administered of antibiotics must be immediate.

Type 2 Diabetes Mellitus and its related foot complications in Malaysia

2009-10-12T02:57:00.000-07:00

Incidence of Type 2 Diabetes Mellitus in Malaysia:

In Malaysia, the First National Health and Morbidity Survey (NHMS 1) conducted in 1986 reported a prevalence of diabetes mellitus of 6.3% [1]. In the Second National Health and Morbidity Survey (NHMS 2) in 1996, the prevalence had risen to 8.3% [2]. The prevalence of diabetes had increased drastically to 14.9 per cent in 2006 for the same age group; an increase of 80% based on the Third National Health and Morbidity Survey 2006 (NHMS 3) [3]. Currently, it is estimated that one out of eight Malaysians aged 30 years and above has diabetes, which amounts to over 1.6 million adults in Malaysia. The World Health Organisation (WHO) has estimated that in 2030, Malaysia would have a total number of 2.48 million diabetics compared to 0.94 million in 2000 - a 164% increase.

Incidence of foot related complications:

Foot ulceration associated with infection is one of the leading causes of hospitalization patients with diabetes mellitus. Approximately 15% of all patients with diabetes will develop a foot or leg ulceration at some time during the course of their disease.[1-3]

Several population-based studies report an annual incidence of diabetic foot ulceration in the range of 2% to 3% in patients with either Type 1 or Type 2 diabetes, while the prevalence varies between 4% and 10%

Numerous risk factors for diabetic foot ulceration have been ascertained. Aside from the major factors of neuropathy, ischemia, pressure (trauma), and infection, multiple other contributory factors interact to produce foot lesions. Intrinsic risk factors include metabolic or biologic characteristics that may or may not be causally related to diabetes but do contribute to the aetiology of ulceration.

Symptom of diabetes:

48% of patients above the age of 30 years old are not aware that they have diabetic. The majority are asymptomatic. Patients should be aware of common symptoms of diabetes which include polyuria (increased frequency of urination), polydipsia (increased thrist), easily tired and sudden unexplained weight loss [4].

Classification diabetic foot complications
Diabetic Foot Problems are best classified according to King’s Classification [5].
Stage 1: Normal
Stage 2: High Risk
Stage 3: Ulcerated
Stage 4: Cellulitic Stage
Stage 5: Necrotic
Stage 6: Major Amputation

Post Ray’s amputation+ incision and drainage

The surgical wound located at the dorsal surface of the right foot. The wound bed consists of granulation tissues and slough. This is not a well-healing wound.

Investigations

Glycosylated hemoglobin level must be taken to obtain information of the patient’s glucose control over the past 3 months. This investigation is based on the fact that in the normal 120 day life span of the red blood cell, excess glucose molecules will react with hemoglobin, forming glycosylated hemoglobin. In individuals with poorly controlled diabetes, the level of glycosylated hemoglobins will be elevated.

Plain radiograph of foot and ankle can also be taken to make sure there is no involvement of bone to rule out osteomyelitis.

Doppler ultrasound also is significant to investigate the peripheral circulation of foot to prevent ischemia.

Diabetic Foot Care Treatment

Self-Care at Home

A person with diabetes should do the following:

Foot examination: Examine your feet daily and also after any trauma, no matter how minor, to your feet. Report any abnormalities to your physician. Use a water-based moisturizer every day (but not between your toes) to prevent dry skin and cracking. Wear cotton or wool socks. Avoid elastic socks and hosiery because they may impair circulation.

Eliminate obstacles: Move or remove any items you are likely to trip over or bump your feet on. Keep clutter on the floor picked up. Light the pathways used at night - indoors and outdoors.

Toenail trimming: Always cut your nails with a safety clipper, never a scissors. Cut them straight across and leave plenty of room out from the nailbed or quick. If you have difficulty with your vision or using your hands, let your doctor do it for you or train a family member how to do it safely.

Footwear: Wear sturdy, comfortable shoes whenever feasible to protect your feet. To be sure your shoes fit properly, see a podiatrist (foot doctor) for fitting recommendations or shop at shoe stores specializing in fitting people with diabetes. Your endocrinologist (diabetes specialist) can provide you with a refferel to a podiatrist ororthopedist who may also be an excellent resource for finding local shoe stores. If you have flat feet, bunions, or hammertoes, you may need prescription shoes or shoe inserts.

Exercise: Regular exercise will improve bone and joint health in your feet and legs, improve circulation to your legs, and will also help to stabilize your blood sugar levels. Consult your physician prior to beginning any exercise program.

Smoking: If you smoke any form of tobacco, quitting can be one of the best things you can do to prevent problems with your feet. Smoking accelerates damage to blood vessels, especially small blood vessels leading to poor circulation, which is a major risk factor for foot infections and ultimately amputations.

Diabetes control: Following a reasonable diet, taking your medications, checking your blood sugar regularly, exercising regularly, and maintaining good communication with your physician are essential in keeping your diabetes under control. Consistent long-term blood sugar control to near normal levels can greatly lower the risk of damage to your nerves, kidneys, eyes, and blood vessels.

Medical Treatment

Antibiotics: If the doctor determines that a wound or ulcer on the patient’s feet or legs is infected, or if the wound has high a risk of becoming infected, such as a cat bite, antibiotics will be prescribed to treat the infection or the potential infection. It is very important that the patient take the entire course of antibiotics as prescribed. Generally, the patient should see some improvement in the wound in two to three days and may see improvement the first day. For limb-threatening or life-threatening infections, the patient will be admitted to the hospital and given IV antibiotics. Less serious infections may be treated with pills as an outpatient The doctor may give a single dose of antibiotics as a shot or IV dose prior to starting pills in the clinic or emergency department.

Referral to wound care center: Many of the larger community hospitals now have wound care centers specializing in the treatment of diabetic lower extremity wounds and ulcers along with other difficult-to-treat wounds. In these multidisciplinary centers, professionals of many specialties including doctors, nurses, and therapists work with the patient and their doctor in developing a treatment plan for the wound or leg ulcer. Treatment plans may include surgical debridement of the wound, improvement of circulation through surgery or therapy, special dressings, and antibiotics. The plan may include a combination of treatments.

Referral to podiatrist or orthopedic surgeon: If the patient has bone-related problems, toenail problems,corn and callus hammertoes, bunions, flat feet, heel spurs, arthritis, or have difficulty with finding shoes that fit, a physician may refer you to one of these specialists. They create shoe inserts, prescribe shoes, remove calluses and have expertise in surgical solutions for bone problems. They can also be an excellent resource for how to care for the patient’s feet routinely.

Home health care: The patient’s doctor may prescribe a home health nurse or aide to help with wound care and dressings, monitor blood sugar, and help the patient take antibiotics and other medications properly during the healing period.

References

1. National Health and Morbidity Survey 1986

2. National Health and Morbidity Survey 1996

3. National Health and Morbidity Survey 2006

4. Mafauzy M. Diabetes Mellitus in Malaysia. Medical Journal of Malaysia. 2006.

5. Edmonds ME and Foster AVM. Managing the diabetic foot, 2nd ed. (Blackwell, London, 2005).

Malaysia endocrine and metabolic society,Ministry of health,acdemic of medicine malaysia,Persatuan diabetic malaysia.

Bionic brain chips could overcome paralysis

2009-09-12T06:33:00.000-07:00

By Sunny Bains

A MONKEY sits on a bench, wires running from its head and wrist into a small box of electronics. At first the wrist lies limp, but within 10 minutes the monkey begins to flex its muscles and move its hand from side to side. The movements are clumsy, but they are enough to justify a rewarding slug of juice. After all, it shouldn't be able to move its wrist at all.

A nerve connection in the monkey's upper arm had previously been blocked with an anaesthetic that prevented signals travelling from its brain to its wrist, leaving the muscles temporarily paralysed. The monkey was only able to move its arm because the wires and the black box bypassed the broken link.

The monkey was in Eberhard Fetz's lab at the University of Washington in Seattle. The experiment, performed last year, was the first demonstration of a new treatment that might one day cure paralysis, which is typically caused by a broken connection in the spinal cord. Though much work has focused on using stem cells to regrow damaged nerve fibres, some researchers believe that an electronic bypass like this is equally viable.

The idea is to implant electronic chips in the relevant regions of the brain to record neural activity. Then a decoder deciphers the neural chatter, often from thousands of neurons, to figure out what the brain wants the body to do. These messages must then be relayed - ideally wirelessly - to electrodes that deliver a pulse of electricity to stimulate the muscles into action. Such "brain chips" are already restoring hearing to the deaf and vision to the blind, and helping to stave off epileptic fits, so the idea isn't as far-fetched as it might sound (see "Bionic medicine").

Every step of progress in tackling paralysis has been hard won. One of the early demonstrations that it may be possible emerged in 2003, when José Carmena, then at Duke University in Durham, North Carolina, successfully created an interface between brain and machine that allowed his lab monkeys to play a computer game using only their minds.

To gain a juice reward, the monkeys had to move a cursor - initially with a joystick - to hit a target on the computer screen. Beforehand, Carmena and his colleagues had implanted several chips throughout the parietal and frontal lobes of the monkeys' brains - regions known to plan and control movement. Each chip held up to 64 electrodes, which recorded the firing of the surrounding neurons as the monkeys manipulated the joystick.

Once the system had successfully decoded the chatter from the monkeys' neurons, the program stopped responding to the joystick's movement altogether and relied solely on the monkeys' thoughts to control the cursor. Eventually even the animals worked this out and stopped holding the joysticks as they completed the task (PLoS Biology, vol 1, p 42).

Manipulating a cursor on a computer screen is one thing, but whether such brain chips could translate the more complicated tasks of daily life remained an open question until 2004, when John Donoghue and colleagues from Cyberkinetics in Providence, Rhode Island, implanted a 100-electrode chip in the brain of a 25-year-old man known as MN, who had been left paralysed from the neck down by a knife wound.

Over the subsequent nine months, MN successfully used this BrainGate chip to open emails, operate a television and even control a robotic arm (Nature, vol 442, p 164). It was a promising step, but the technology was far from perfect. "Although BrainGate1 worked well in many ways, at times the control was not satisfactory," says Donoghue. And by the end of the trial, fluids from the brain had degraded the chip. The team are now solving these problems, and earlier this year announced the start of a clinical trial for an improved version of the chip.

With a chip implanted in his brain, a paralysed man was able to open emails, operate the TV and even control a robotic arm

The ultimate hope for many paralysed people, of course, is to regain movement in their own limbs. Until Fetz's experiment last year, no one had successfully used an implant to bridge a broken connection between the brain and the body. Trials of functional electrical stimulation (FES), in which implanted electrodes directly stimulate muscles into action, had hinted that this might be possible. But these impulses had been activated by external triggers, such as a switch controlled by one of the patient's healthy limbs, and not directly by brain signals.

Not only did Fetz's work demonstrate that the electronics could descramble neural signals and relay appropriate instructions to the limbs using FES, he also showed that the brain makes the job easier than one might expect. Although the motor neurons that connected to the chip did not naturally control the wrist, in a short time they adapted to the task and controlled complex actions (Nature, vol 456, p 639). "All neurons could be used equally well for control regardless of their original association to movement," says team member Chet Moritz.

That could have an important implication for humans hoping to use similar implants in the future. "It underscores the impressive flexibility of the brain in learning to adapt to novel connections, which may play a key role in allowing neural prostheses to be adopted by patients," he says.

So could the same approach work in humans? There seem to be no fundamental obstacles, and Donoghue plans to test the proposition in the new BrainGate trials, using his chip to control a limb using FES. If successful, it will represent a milestone in the development of such treatments.

Direct electrical stimulation of muscles using FES is unlikely to be the final solution, however. This direct approach uses a relatively powerful electric current applied to large areas of tissue, producing fairly clumsy movements. A more elegant method, some claim, is to send the impulse along the existing healthy nerves. That would require smaller local currents, delivered with greater precision, to finer regions of the muscle tissue, which should allow more subtle control.

Coordination

As a bonus, nerve stimulation could simplify some of the demands placed on a brain chip. That's because for many rhythmic activities, such as breathing, walking and crawling, the brain simply sends a command signal and it is the spinal cord's in-built systems that orchestrate the fine movements of each muscle. So if the healthy sections of a damaged spinal cord have retained their ability to control movement, the electronic chip could transmit the brain signal around the broken connection but leave the muscular orchestration to the spinal cord. In this case, a brain chip would just beam the message to a second device implanted in the spine below the break, which would then stimulate the spinal cord.

The chips could simply transmit the information around the break, leaving the undamaged sections of the spinal cord to orchestrate the muscles

That could "dramatically simplify the control signals needed from the brain", says Moritz, since for these repetitive tasks the brain chip would just decode and transmit an umbrella command. Such simplification should make the chips less likely to fail - an important consideration when the only way to replace the chips is through invasive surgery - and also reduce their power consumption.

Using this principle in 2002, Vivian Mushahwar, now at the University of Alberta in Edmonton, Canada, plugged four electrodes into a cat's spinal cord and delivered signals that mimicked the brain's command to walk. Sure enough, the cat made stepping motions.

Simply relaying the messages across a break in this way would not help the worst injuries, however, in which the spinal cord has lost its ability to coordinate muscles. In these cases, to minimise the size of the brain chip, and the burden placed on it, the muscular orchestration would need to come from either the chip implanted in the spinal cord, or an external device that communicates wirelessly with the chips in the brain and the spine.

Calculating exactly which nerves to stimulate and in what pattern is no easy task, but the first demonstration of an artificial "central pattern generator" was reported last year, when Mushahwar and colleagues at Johns Hopkins University in Baltimore, Maryland, successfully tested such a chip on a cat. With coordination coming solely from an external CPG chip connected to a handful of electrodes that stimulated the cat's spine, the animal was able to walk (IEEE Transactions on Biomedical Circuits and Systems, vol 2, p 212). In this experiment, the team were simply testing the CPG's ability to orchestrate movement as an alternative to FES, so the trigger came from a manual switch and not the cat's brain. The next hurdle will be to use the CPG in conjunction with a neural chip.

While this CPG chip only dealt with the action of walking, in humans an additional external chip might also offload some of the processing from the brain chip for non-repetitive motions like clenching a fist or raising a hand. The brain doesn't necessarily produce an umbrella command for all of these movements, so the neural implant would still need to detect a more complicated signal, but the external chip could at least perform some of the processing to decode and relay these comands to the relevant electrodes.

For many patients, technology like this would only solve half the problem, however. Paralysed people who have lost feeling as well as movement in their limbs would need two-way systems to pass sensations back to their brain. This information could come from artificial sensors, but ideally the chip would read sensations from existing nerves and relay them to chips that stimulate the areas of the brain that process tactile information.

Although work has been slower in this area, there's good evidence it will one day be possible. Carmena, for instance, who is now at the University of California, Berkeley, recently stimulated a rat's brain to feel sensations from some "virtual whiskers", causing it to move as if its own whisker's had really brushed against an object. Similar technology could one day relay tactile information to the human brain.

If these advances in brain-chip capability are to be exploited, the researchers still need to ensure that the chips are safe and durable. Biocompatibility, for instance, is a huge challenge, because tissue in the brain can react badly to an implant, killing off the very neurons that the electronics are trying to connect to. Recent efforts suggest a coating of growth hormones might mitigate this problem, while others have shown chips that slowly exude stem cells might also work.

Then there's the problem of powering the devices. Most existing implants - like cochlear implants, for example - are connected to a battery outside the head that can be replaced regularly. The electrodes in the spine and limbs could be powered this way, but it's less practical for a chip deep within the skull. Instead, such chips will need to be recharged by electromagnetic fields generated by a device outside the head, so power consumption will have to be minimal.

One solution might be to offload the more difficult processing to a portable computer outside the body, before passing the information back to the chips that stimulate the nervous system. In this way, Reid Harrison at the University of Utah in Salt Lake City has produced a neural chip that uses just 8 milliwatts. That's less than the "standby" LED on the front of a TV set.

Security risks

All the pieces are gradually coming together, but whatever happens it will be a long time before these chips can become a mainstream treatment: the US Food and Drug Administration requires as much as 10 years of animal testing before a chip can be deemed safe enough to be implanted in human brains. That means the latest technology, such as chips that stimulate tactile sensations in the brain, will need extensive testing before clinical trials can begin.

Yet even once the technology has proven itself, the social issues surrounding the treatment will need to be solved. Take the question of security, for example. Last year, a team of researchers successfully hacked into a heart pacemaker and defibrillator through the wireless communication that allows doctors to adjust its performance. Although the device wasn't implanted in anyone at the time, it raised the possibility that hackers could disrupt a patient's treatment (New Scientist, 22 March 2008, p 23).

To make matters worse, there is currently no obvious way of protecting a defibrillator or pacemaker from a hacker without inhibiting a doctor from accessing it during an emergency. Since neural prostheses will rely so heavily on wireless links to communicate between the different components, the risk to these chips may be even greater.

Perhaps most perplexing is the question of legal responsibility. If someone wearing a neural prosthesis were to punch someone, who is to blame? The action may have been deliberate, in which case the patient is to blame, or the chip may have been malfunctioning and the responsibility would lie with the manufacturer. Discovering where the truth lay would be no easy task. The law has had trouble catching up with the self-parking car, never mind an electronically controlled limb gone wild.

Bionic medicine

Paralysis is not the only condition that can be treated with chips in the brain

Deafness

The cochlear implant has been commercially available for many years. It detects sound and creates a signal that is fed directly into the auditory nerve. In this way, damaged portions of the ear can be bypassed entirely.

Blindness

Retinal prostheses are being tested in blind people who lack the ability to turn light signals into neural signals. They can be plugged into the brain either at the retina itself, the optic nerve, or even the visual cortex.

Parkinson's disease

Some people with Parkinson's are implanted with deep brain stimulation systems that can prevent some of the shaking that is characteristic of the disease. Though the surgery carries risks, a new study shows that people gained more than 4.5 "good" hours a day using the devices (The Journal of the American Medical Association, vol 301, p 63).

Epilepsy

Devices known by some as "brain pacemakers" send regular electrical pulses to parts of the brain associated with the condition, helping to prevent the neurons from firing in the patterns associated with seizures.

Sunny Bains is a science journalist based in London

Diabetic foot team lowers rate of major amputations

2009-09-12T00:41:00.000-07:00

Incidence of major diabetic foot amputations decreased 41% in 10 years.

By Gina Brockenbrough
ORTHOPAEDICS TODAY EUROPE 2009; 12:17

Norwegian investigators discovered a significant decrease in the incidence of diabetic foot amputations in one town 10 years after the establishment of a diabetic foot team at the city’s only hospital.

“We have registered a 41% decrease in major diabetic amputations,” Eivind Witsø, MD, said during his presentation at the 10th EFORT Congress. “The decrease reflects the improved quality of the prevention and treatment of diabetic foot ulcers and a general improvement in public health.”

In a previous study of patients with diabetes in the city of Trondheim, Norway, Witsø and his colleagues identified a rate of 4.4 lower extremity amputations per 1,000 patients each year between 1994 and 1997 — a rate he considered high.

Diabetic foot team lowers rate of major amputations

Incidence of major diabetic foot amputations decreased 41% in 10 years.

By Gina Brockenbrough
ORTHOPAEDICS TODAY EUROPE 2009; 12:17

Diabetic foot team

In response, the investigators established the Trondheim Diabetic Foot Team as part of the orthopaedic surgery department at St. Olav’s University Hospital. The team consisted of an orthopaedic surgeon, nurse, podiatrist, prosthetist and orthotist, and focused on preventative care and early treatment.

The investigators compared the incidence of diabetic amputations from 1994 to 1997 with information from 2004 to 2007.

Eivind Witsø

Amputations

The investigators found that the overall incidence of diabetic amputations per 1,000 patients with diabetes per year significantly decreased from 4.4 to 2.8 in 10 years.

Although they found that the incidence of minor diabetic amputations also decreased, the difference was not statistically significant.

Witsø said the study revealed no significant difference in the number of vascular interventions performed on patients with diabetes during the decade. He also noted that the diabetic foot team screened nearly 750 patients and performed nearly 6,000 consultations between 1996 and 2006.

A global trend?

During the paper discussion, co-moderator Per Kjaersgaard-Andersen, MD, asked Witsø if there has been a global decrease in the incidence of diabetic amputation.

“No, it’s not a global observation,” Witsø responded. He noted that while some countries have seen a decrease, diabetic foot amputation remains a major problem in other nations. He added that other researchers have observed a decline in diabetic amputations due to preventative care and an increase in vascular interventions.

“Perhaps this is one of the first studies that has shown a decrease in amputations that cannot be explained by an increase in vascular interventions,” Witsø said.

For more information:
Per Kjaersgaard-Andersen, MD, heads the Section for Hip and Knee Replacement, Department of Orthopaedics, Vejle Hospital, DK-7100 Vejle, Denmark; +45-7940-5716; e-mail: pka@dadlnet.dk. He has no direct financial interest in any products or companies mentioned in this article.
Eivind Witsø, MD, can be reached at St. Olav’s University Hospital, Norwegian University of Science, Gate 17, N-7006 Trondheim, Norway, 7030; +47-738-68000; e-mail: eivind.witso@stolav.no. He has no direct financial interest in any products or companies mentioned in this article.

Reference:

Eivind W, Arne L, Stian L. Forty percent decrease in the incidence of diabetic amputations in 10 years. Paper F197. Presented at the 10th EFORT Congress. June 3-6, 2009. Vienna.

Pine Bark Study Shows Further Progress Against Osteoarthritis

2009-09-01T07:06:00.001-07:00

A new study on pine bark as an osteoarthritis treatment showed Pycnogenol reduced osteoarthritis (OA) symptoms by 56% and provided pain relief. In the study, held at Italy’s Chieti-Pescara University, 156 patients with knee OA received 100 milligrams of Pycnogenol or placebo daily for three months and were evaluated using a number of tools. Patients were permitted to continue taking their choice of pain medication provided they recorded every tablet in a diary for later evaluation. Results indicated Pycnogenol, an antioxidant plant extract from the bark of the French maritime pine tree, was an effective OA treatment and provided OA pain relief. In addition, the Pycnogenol group also:

• Experienced a 55% improvement in joint pain.
• Reduced pain medication use by 58%.
• Had a 63% improvement in gastrointestinal complications.
• Reduced stiffness by 53%.
• Improved physical function scores by 57%.
• Enhanced overall well being by 64%.

“The results of this study are significant as they clearly demonstrate the clinical action of Pycnogenol on OA and management of symptoms,” said Gianni Belcaro, a lead researcher of the study. “The use of Pycnogenol may reduce costs and side effects of anti-inflammatory agents and offer a natural alternative solution to people suffering from OA.”

Bio-Spacers

2009-09-01T07:00:00.000-07:00

The Bio-Spacers Range from Orthopaedic Innovation Limited

The Bio-Spacers range from Orthopaedic Innovation Limited, a member of the Medsmart Solutions family, are innovative and highly effective devices designed to help overcome arthroplastic infections, whilst maintaining mobility and the quality of life for the patient.

These temporary, implantable devices, which incorporate Gentamicin, are used to provide a replacement for a joint prosthesis which has been removed as a result of a septic process. They release antibiotic into the surrounding tissues to help the treatment of infected total joint replacement and facilitate successful re-implantation of the definitive prosthesis.

Our range of Bio-Spacers are made from O-I Bone Cement and the Hip Spacer is reinforced with a Stainless Steel (316L) insert to enhance strength. All our spacers feature highly polished surfaces to prevent lesions to joint surfaces and various models and sizes are available. O-I Bio-spacers’ key features are:

Maintenance of joint space, mobilisation and limb length (Partial weight- bearing and functional use of the limb must be assessed on an individual patient basis).
Effective in-situ release of high local antibiotic dosage with reduced systemic effects.
Homogeneous distribution of antibiotic in the cement.
Implantable with bone cement.
Improved quality of life between surgeries.
Eventual easier re-implantation of the definitive prosthesis.
Shorter hospitalisation.
Lower costs per treatment.
Improved recovery index.

http://www.orthopaedicinnovation.com/

Interferon Regulator Factor-8

2009-09-01T06:35:00.000-07:00

Orthopaedics Today

Researchers identify protein involved in causing osteoporosis, arthritis

1^st on the web (August 31, 2009)

Investigators at the Hospital for Special Surgery in New York, along with several collaborators, reported that a gene called interferon regulator factor-8 (IRF-8) plays an important role in the development of diseases such as rheumatoid arthritis, osteoporosis and periodontitis (gum disease).

The study, which appeared online Aug. 30 ahead of print in the journal Nature Medicine, could lead to new treatments, according to the authors.

“The study doesn't have immediate therapeutic applications, but it does open a new avenue of research that could help identify novel therapeutic approaches or interventions to treat diseases such as periodontitis, rheumatoid arthritis or osteoporosis,” Baohong Zhao, PhD, lead author of the study and a research fellow in the Arthritis and Tissue Degeneration Program at the Hospital for Special Surgery, said in a press release.

Zhao initiated the study while working in the laboratory led by Masamichi Takami, PhD, and Ryutaro Kamijo, PhD, at Showa University, Tokyo, where much of the work was performed. Zhao completed the study and extended the work to human cells during the past year at the Hospital for Special Surgery while working with Lionel Ivashkiv, PhD.

Specifically, the researchers discovered that downregulation of IRF-8 increases the production of cells called osteoclasts that are responsible for breaking down bone. Enhanced development of osteoclasts can create canals and cavities that are hallmarks of diseases such as periodontitis, osteoporosis and rheumatoid arthritis.

Previous researchers have spent time identifying genes that are upregulated during enhanced development of osteoclasts, such as NFATc1, but few studies have identified genes that are downregulated in the process, according to the press release.

To fill this knowledge gap, the researchers used microarray technology to conduct a genome-wide screen to identify genes that are downregulated during the formation of osteoclasts. They found that expression of IRF-8 was reduced by 75% in the initial phases of osteoclast development. The researchers then genetically engineered mice to be deficient in IRF-8 and gave the animals X-rays and CT scans to analyze IRF-8's influence on bone.

They found that the mice had decreased bone mass and severe osteoporosis. Experiments demonstrated that this was due not to a decreased number of osteoblasts but rather due to an increased number of osteoclasts. The researchers concluded that IRF-8 suppresses the production of osteoclasts.

Tests in human cells confirmed these findings, Zhao noted.

“This is the first paper to identify that IRF-8 is a novel key inhibitory factor in osteoclastogenesis [production of osteoclasts],” Zhao said in the press release. “We hope that the understanding of this gene can contribute to understanding the regulatory network of osteoclastogenesis and lead to new therapeutic approaches in the future.”

Reduced BMD in adults with very low birth weight may lead to osteoporosis, related fractures

2009-08-31T06:35:00.000-07:00

Orthopaedics Today

1^st on the web (August 28, 2009)

Individuals who had a very low birth weight (VLBW) had significantly less bone mineral density (BMD) at the adult age when they should normally reach peak bone mass compared to same-aged adults born at term, Finnish researchers found.

In the Helsinki Study of Very Low Birth Weight Adults, a multidisciplinary cohort study designed to see if health problems in VLBW babies persist into adulthood, Petteri Hovi, MD, and colleagues evaluated 144 adults between 18.5 and 27.1 years old born in the greater Helsinki area between 1978 and 1985 with VLBW. They compared the group’s skeletal health to 139 adults matched for age, gender and birth hospital.

Hovi and colleagues defined VLBW babies as those whose birth weight was less than 3.31 pounds.

The researchers determined each participant’s BMD using dual-energy X-ray absorptiometry. They calculated Z scores representing the participants’ lower lumbar spine and hip BMD, defining reduced BMD as a Z score of -1.0 units or less.

The study group’s average Z score for the lower lumbar spine was -0.51 unit (95% CI: 0.28-0.75); the average femoral neck Z score was -0.56 unit (95% CI: 0.34-0.78) for areal BMD. After adjusting for the shorter adult height and less intense level of exercise practiced in the VLBW group, the differences remained statistically significant, according to a press release.

“Furthermore, 44% of the VLBW participants, but only 26% of the term-born participants, had a lumbar spine Z score of -1.0 or less,” study editor Tom W.J. Huizinga, of Leiden, Netherlands, wrote in his summary of the findings.

Hovi and colleagues said in their abstract, “This finding may predict symptomatic osteoporosis and increased fracture rates.”

In addition, increased vigilance in osteoporosis prevention may be warranted in VLBW children who become adults with low BMD, they noted.

Researchers said the main limitations of the study were the final cohort may not be representative of the original cohort of individuals born in Helsinki-area hospitals; comparisons they made were only internal; and they measured BMD just once, which reduced the chances of associating lower BMD with other possible causes, such as delayed skeletal maturing in the VLBW group.

Reference:
Hovi P, Andersson S. Järvenpää A-L, et al. Decreased bone mineral density in adults born with very low birth weight: A cohort study. PloS Med. 2009;6(8):e1000135. DOI: 10.1371/journal.pmed.1000135.

Orthopedic study suggests knee extensor strength plays a part in keeping osteoarthritis at bay

2009-08-31T06:27:00.000-07:00

Orthopaedics Today

1^st on the web (August 27, 2009)

Researchers exploring factors that affect the risk of developing symptomatic knee osteoarthritis in a multicenter study found that women with the strongest thigh muscles developed the condition less often than women with weaker knee extensor strength.

According to findings from the Multicenter Knee Osteoarthritis Study, funded by the U.S. National Institute on Aging, men with stronger thigh muscles were only slightly more protected from developing symptomatic OA than those with weaker muscles. Furthermore, thigh muscle strength was not helpful for predicting radiographic OA in women or men, the investigators noted in their study, which appears online today in Arthritis Care & Research.

“These findings suggest that targeted interventions to reduce risk for symptomatic knee OA could be directed toward increasing knee extensor strength,” co-investigator Neal A. Segal, MD, MS, from the department of orthopedics and rehabilitation at the University of Iowa, said in a press release.

Segal and colleagues studied the knees of 3,026 men and women 50 to 79 years old. They measured study participants’ thigh muscle strength with a dynamometer and determined their H:Q ratio, an indication of the balance of strength between hamstrings and quadriceps.

Investigators followed subjects 30 months using knee radiographs and telephone interviews to establish baseline OA, pain and other knee symptoms with the goal of determining whether knee extensor strength was a predictor of radiographic or symptomatic knee OA.

To draw their conclusions, they took into account the participants’ height, weight, body mass index, femoral neck bone mineral density and self-assessed level of physical activity.

At the end of their study, investigators reported that 7.1 % of men and 9.9% of women developed radiographic knee OA, compared to 7.8% of men and 10.1% of women who had signs of symptomatic OA. “H:Q ratio was not predictive of symptomatic knee OA in either men or women,” they wrote in their results.

The lack of hip abductor strength assessments in the analysis was one of the study limitations, the researchers noted in the press release.

“Study of hip abductor strength, which is important for control of the knee joint, may be useful in a more comprehensive study of risk for OA of the knee,” Segal said in the release.

Reference:
Segal NA, Torner JC, Felson D, et al. Effect of thigh strength on incident radiographic and symptomatic knee osteoarthritis in a longitudinal cohort. Arthritis Care Res. Published online Aug. 27, 2009 (DOI 10.1002/art).

Limb-sparing surgery and amputation provide similar quality of life for patients with bone cancer

2009-08-25T08:54:00.001-07:00

1^st on the web (August 11, 2009)

Limb-sparing surgery, an alternative to amputation for bone and soft tissue sarcomas of the lower limb, may not provide much or even any additional benefit to patients compared to amputation, according to a new review.

Researchers who conducted the analysis, which was posted yesterday in the online edition of Cancer, recommend that patients and physicians should rethink the pros and cons of both limb-sparing surgery and amputation before making a final decision.

To compare the costs and benefits of limb-sparing surgery with amputation in these patients with cancer, researchers Ronald Barr, MD, MB, ChB, of McMaster University in Hamilton, Ontario, and Jay Wunder, MD, MSc, of Mount Sinai Hospital and the University of Toronto, reviewed all published papers on limb-sparing surgery that also measured patients’ functional health and quality of life.

According to a press release, the researchers found that while limb-sparing surgery is generally as effective as amputation in removing the patient’s cancer, it tends to be associated with more early and late complications. Studies also show that, particularly for patients with lower limb bone sarcomas, limb salvage does not provide a better quality of life to patients than amputation, according to the press release.

In the press release, Wunder said most studies have found that the differences in disability between amputation and limb-sparing patients are smaller than expected. Many revealed no significant differences in psychological health and quality of life between patients who underwent amputations and those who had limb-sparing surgery. However, there appear to be greater advantages to limb-sparing surgery over amputation for higher surgical sites in the lower limb, such as the hip.

Some studies have compared the costs of amputation vs. limb-sparing surgery. “Up front” surgical costs, the duration of rehabilitation and the need for revisions are all greater for limb-sparing surgery. However, amputation carries greater longer-term costs related to artificial limb manufacture, maintenance and replacement, the researchers said in the press release.

The authors say additional research is needed to provide a thorough comparison of amputation and limb-sparing surgery in different types of patients with bone and soft tissue sarcomas.

“Future studies that include function, health-related quality of life, economics and stratification of patients by age will be useful contributions to decision-making … by patients, health care providers and administrators,” Wunder said in the press release.

Reference:
Barr R, Wunder J. Bone and soft tissue sarcomas are often curable – But at what cost? A call to arms (and legs). Cancer. Advance preview published on Aug. 10. 10.1002/cncr.24458.

Promising results seen with minimally invasive repair of Achilles tendon ruptures

2009-08-25T08:52:00.001-07:00

Surgeon cautions that device may not benefit tendon rupture cases with frayed ends.

By Gina Brockenbrough
ORTHOPEDICS TODAY 2009; 29:42

DENVER — With minimally invasive surgical repair of Achilles tendon ruptures, surgeons look to obtain the advantages of open repair techniques while avoiding the problems of wound complications and infections.

At the American Orthopaedic Foot and Ankle Society’s 24th Annual Meeting, Eric M. Bluman, MD, PhD, discussed the results of minimally invasive repair techniques and highlighted the outcomes of repairs using a minimally invasive Achilles tendon suture device (Achillon, Integra).

“I think that minimally invasive repairs have shown promising results in case series and limited level I studies,” Bluman said. “Obviously, more level I studies are needed, and I think that we need to show caution in using [the Achillon] technique. It may be particularly difficult to use in ruptures in which the tendon ends are frayed or in very distal ruptures where tendon material in which to put your sutures in is limited.”

Tendon suture device

Although his presentation focused on minimally invasive repairs, Bluman use nonoperative treatment for Achilles tendon ruptures when indicated and open repair on occasion. Regarding surgical methods, “I began questioning how I could justify the assault on the posterior tissues in the ankle, when there are methods to obtain repairs with much less invasive methods,” he said.

The minimally invasive repair technique he uses is aided by the Achillon device. The technique uses a 2-cm vertical incision that allows for direct visualization of tendon apposition. It also maintains all the sutures deep to the peritenon, Bluman said. “One of the nice things about the vertical incisions is it is easily converted into an open approach if needed.”

Image showing the scar left after a minimally invasive Achilles tendon rupture repair.

Image: Bluman EM

Bluman said he has used the technique on many patients, 11 of whom have a minimum 1-year follow-up. “All are back to their pre-rupture activity level,” he said. “These are active duty military people and active retirees. All patients are satisfied and would have the procedure again.”

Comparing the uninjured side to the contralateral limb using dynamometry showed no significant difference, he said. He noted no wound problems, infections, re-ruptures, sural nerve injuries or adhesions were seen.

No infections, nerve injuries

A study by the device’s inventor reported on 83 patients whose tendons were repaired using the Achillon device showed no infections and no sural nerve injuries, Bluman said. “They did have three re-ruptures which they attributed to noncompliance of the patients, and all of their patients did eventually return to previous function.”

He also cited an independent study performed by Calder, and colleagues which corroborated the results with the device in 25 patients. The investigators found no infections, wound dehiscence, sural nerve injuries or re-ruptures and reported good functional results.

Although totally percutaneous techniques reduce infection and wound dehiscence rates to 0%, “There have been reports of increased rates of sural nerve injury as high as 17% in some cases,” Bluman said. “There is an inability to directly visualize tendon apposition as well.” Sural nerve injuries have been shown to be due to lassoing of the nerve with the suture in percutaneous cases.

In a study comparing percutaneous and open repair, Lim and colleagues found two adhesions, two re-ruptures and a 21% infection rate in the open repair group. In the percutaneous cohort, they had one re-rupture, one sural neuropathy and had three cases of wound puckering. “This study was limited in that no dynamometry was done and only subjective outcome measures were used for evaluation,” Bluman said.

For more information:
Eric M. Bluman, MD, PhD, can be reached at Madigan Army Medical Center, Orthopaedic Surgery, 9040 A. Fitzsimmons Fr., Tacoma, WA 98431; 253-968-1581; e-mail: emb43@cornell.edu. He receives miscellaneous non-income support from DePuy.
Reference:
Bluman EM. Minimally invasive surgical repair of the Achilles tendon rupture. Presented at the American Orthopaedic Foot and Ankle Society 24th Annual Summer Meeting. June 26-28, 2008. Denver.

Total Hip Replacement and Hip Resurfacing Surgery

2009-08-25T08:39:00.000-07:00

Source: http://www.bananarepublican.info/Hip_Surface_Replacement.htm

Background

Hip replacement surgery has been around since the early 1960s. Sir John Charnley experimented in the early 1950s, and he used a small (22 mm) stainless steel ball on a stem in 1962 that he inserted into the femur (hip) bone to replace the femoral head (ball). He then inserted a high-density plastic socket to replace the acetabular (socket) side of the hip joint. Both were secured with a self-curing acrylic polymer known as bone cement.

Total Hip Replacements

Today, the modular balls are made of a cobalt-chrome metal alloy or a ceramic material, and some of the components are press-fit and do not require bone cement. The procedure remains basically the same: (1) the femur bone is amputated to remove the femoral head; (2) the femoral canal is reamed-out for insertion of the stem; (3) an acetabular socket is affixed to the socket side of the hip; and (4) the ball joint is inserted into the acetabular socket. This is known as a total hip replacement, or more correctly, total hip arthroplasty (THA).

image from www.wmt.com

(Click on image to enlarge)

image from www.jri-oh.com

(Click on image to enlarge)

image from www.jri-oh.com

(Click on image to enlarge)

The acetabular socket used in THA is normally lined with a high molecular weight polyethylene (sometimes the liner is ceramic). A metal or ceramic ball is attached to the stem and rotates within the socket. Fine particulate debris is produced from the wearing process of the ball against the liner that leads to tissue reaction. The body’s immune system attacks the debris, and consequently, attacks the adjacent bone supporting the THA device, leading to bone loss and a loosening of the device. This bone loss is known as osteolysis. To lessen the amount of wear, a small ball (approximately 30 mm) is used; however, the small size of the ball makes the joint less stable and increases the risk of dislocation in certain circumstances.

The loosening of the THA device requires revision surgery in which a larger diameter stem must be inserted in the femoral canal. Depending on the age and activity of the patient, multiple revision surgeries may be necessary throughout a patient’s life. A young (under 60), active individual can expect only 10 – 15 years before needing revision surgery. Revision surgery can be complex and costly. The lifespan of a THA device is clocked in miles rather than years.

(Note: Wright Medical Technology, Inc. has developed a large femoral head using metal-on-metal technology (see Hip Surface Replacement below) that reduces the risk of dislocations and osteolysis in THRs. The large head THR has received FDA approval and is actively being marketed.)

Hip Surface Replacements

Although it was experimented with and attempted in the 1960s, metal-on-metal “resurfacing” of the femur and acetabulum was abandoned because of loosening of the fittings. With the refinement of acrylic fixation and its very successful use with the THA stem, interest in hip resurfacing was renewed, and it was subsequently used in several countries in the 1970s. (See History of Hip Resurfacing.)

Resurfacing has the advantage of preserving the femoral bone stock (and marrow contained in the femur). It also has the advantage of easy future revision to THA if it becomes necessary. Since the femur is persevered and not amputated in the initial hip surface replacement surgery, it is available to support a THA stem should revision become necessary. Maintaining the integrity of the femur bone also aids in the mechanical transfer of weight and stress in a more natural manner. Where THA patients often experience thigh pain, recipients of hip surface replacements avoid that particular discomfort.

image from www.jri-oh.com

(Click on image to enlarge)

image from www.jri-oh.com

(Click on image to enlarge)

Using a metal acetabular socket as well as a metal cap over the femur head (metal-on-metal) eliminates the polyethylene debris produced in THA. The metal wear debris from a hip surface replacement produces smaller particles than polyethylene wear debris. The inflammatory response to metal debris is considerably less than that from polyethylene debris. It is believed that the body can partially dissolve and expel metal since it is a naturally occurring substance in the body. There is concern by some of the toxicity of metal, but there is currently no definitive evidence that metal ions cause cancer. Since a metal surface does not wear as readily as a polyethylene lining, a larger ball (approximately 38-51 mm) can be used that adds stability to the joint and reduces the danger of dislocation.

images from www.wmt.com & www.jri-oh.com

(Click on images to enlarge)

The surgery time for hip surface replacement is slightly longer than that for THA. The attachment of the acetabular socket is basically the same. It is press-fitted and does not require bone cement. The attachment of the cobalt-chrome cap requires a more precise alignment, and it takes slightly longer to fit. The hole for the pin insertion must be aligned and drilled, and the dome of the femoral head must be ground and shaped to fit the cap. Some bone cement is used to affix the cap, but the interior surface of both the cap and the socket is such that bone grows into the relief surface to grip the device. (See the video clips of hip resurfacing surgery.)

The following images are from an Instructional Lecture delivered at an International Symposium in Fukuoka, Japan on March 16, 1996 by Harlan C. Amstutz, Peter Grigoris, and Frederick J. Dorey entitled "Evolution and future of surface replacement of the hip." Journal of Orthopaedic Science. J Orthop Sci (1998) 3:169-186.

Superimposed hemisurface. Pin centering guide. Cylindrical reamer.

Saw cutoff guide and oscillating saw. Chamfered reamer. Femoral head bone preparation.

(Click on images to enlarge)

Risks involved in the hip surface replacement surgery are the same as the risks involved in any major surgery. Risks specific to the hip surface replacement involve the potential for cracking in the neck of the femur bone due to the drilling of the guide hole through the neck for the support pin in the metal cap, and also a negative reaction of the femur head to dislocation and being reshaped to fit the metal cap leading to the development of avascular necrosis (bone death)--often referred to as AVN--due to a disruption of blood circulation to the femur head and neck (see AVN Risk). In such instances, a THA could easily be performed to correct the problem.

Hip surface replacement in the United States has been pioneered by Harlan C. Amstutz, M.D. at the Joint Replacement Institute in Los Angeles, CA. For years, a hip surface replacement in the United States has been labeled an “investigative device” by the Food and Drug Administration (FDA). The longest study has been conducted by Wright Medical Technology, Inc. under the product name of CONSERVE ® Plus Total Resurfacing Hip System. The clinical trials have proceeded for a number of years, and they are nearing their end. They have involved nine surgeons across the country in California, Florida, Texas, Maryland, North Carolina, Ohio, and in the Pacific Northwest. Corin Medical, Ltd. of the United Kingdom has also begun an FDA study in the United States using the Cormet 2000 device.

Click here to read the 2-6 year follow up report of the first 400 CONSERVE ® Plus hips.

In Europe, the Birmingham Hip Surface Replacement System (BHR) has been in use for many years. Smith & Nephew Inc., manufacturer of the BHR, applied for FDA approval, and perhaps due to the long record of use in Europe, they obtained FDA premarket approval to begin commercial distribution of their device in the United States on May 9, 2006 (see FDA approval letter and FDA announcement). Because the BHR was not previously used in the United States, the number of American surgeons qualified to use it was limited due to the fact that they had all been participating in the Wright and Corin studies; however, that is destined to change with the FDA approval obtained by Smith & Nephew.

Hospital for Special Surgery lays claim to being the oldest U.S. orthopedic hospital

2009-08-25T08:27:00.000-07:00

The 162-bed hospital is known for achievements in sports medicine, joint replacement and research.

By Susan M. Rapp
ORTHOPEDICS TODAY 2009; 29:58

The 146-year history of Hospital for Special Surgery is rich with clinical, research and educational accomplishments that have improved how orthopedic medicine is practiced.

In 1863, Hospital for Special Surgery (HSS) in New York began as the Hospital for the Ruptured and Crippled in a philanthropic effort to provide medical care to injured Civil War soldiers and needy city residents. It has been led by 11 surgeons-in-chief and now has 85 full-time orthopedic surgeons who performed 24,000 orthopedic procedures in 2008, including more than 7,366 joint replacements, according to current HSS Surgeon-in-Chief Thomas P. Sculco, MD.

The list of musculoskeletal medicine pioneers from HSS reads like a who’s who of orthopedic innovation: Harlan C. Amstutz, MD, Albert Burstein, PhD, John N. Insall, MD, Chitranjan S. Ranawat, MD, Peter S. Walker, PhD, and Russell E. Warren, MD, among others.

“The many strong physician contributors at HSS over the years are typified by how well they integrated excellent patient care with critical review and analysis of clinical results and applied, basic science,” said Douglas W. Jackson, MD, Chief Medical Editor of Orthopedics Today.

Hospital for Special Surgery (HSS) is an independent, free-standing orthopedic hospital that is closely affiliated with a medical center and the Weill Cornell Medical College for conducting musculoskeletal research.

Images: Hospital for Special Surgery

Leading the way

“We are the oldest orthopedic hospital, certainly in the United States and probably in the world,” Sculco said.

HSS was founded by the first surgeon-in-chief, James Knight, MD, whose interest in orthopedics was limited to designing and constructing braces for children’s congenital deformities.

Eventually HSS’ focus shifted entirely to the treatment and rehabilitation of the musculoskeletal system for patients locally and around the world, which remains the mission of the 162-bed hospital. HSS also has

Surgical innovation

An early HSS pioneer, Virgil P. Gibney, MD, became the second surgeon-in-chief in 1887 and held the position 40 years. He instituted changes in the work performed at the hospital and wrote about hip surgery.

“Virgil Gibney was responsible for establishing the first orthopedic residency,” in the 1890s, Sculco told Orthopedics Today.

“He put the hospital on the map as a surgical hospital,” said David B. Levine, MD, Director of HSS Alumni Affairs.

The first HSS Surgeon-in-Chief James Knight, MD, founded the hospital in 1863 at his home in lower Manhattan. He was a general physician rather than an orthopedic surgeon.

The late John Marshall, MD, a physician at HSS, is credited with launching sports medicine as an academic discipline.

Gibney’s leadership

Gibney was the first president of the American Orthopaedic Association.

Under Philip D. Wilson Sr., MD, who became the fifth surgeon-in-chief in 1935, the hospital changed its name to The Hospital for Special Surgery, moved to its current site and affiliated with Weill Cornell Medical College. In 1996, HSS dropped “The” from the beginning of its name.

“Wilson, Sr. had the vision to make it a very specialized institution and improve its research and academic mission,” Sculco said.

Wilson was AAOS president in 1934. His son, Philip D. Wilson Jr., MD, was the eighth surgeon-in-chief and AAOS president in 1972.

Knee arthroplasty

Wilson Jr. bridged the gap between engineering and biomechanics, according to Sculco.

“He created an environment here in the late 1960s and early 1970s for the design and development of implants with surgeons collaborating closely with engineers and basic scientists. To a large extent, that still goes on today.”

The joint arthroplasty research work performed by engineers like Walker and Burstein exemplifies that collaboration, yielding the duo-condylar knee developed in 1971. In 1973 Walker broached the concept of the cemented cruciate-sacrificing total condylar knee prosthesis that improved on other available designs.

Burstein and Insall developed the first posterior stabilized knee prosthesis in 1979 and in 1989 an updated version was marketed.

Subspecialization

In the 1970s, “[Wilson, Jr.] reorganized the orthopedic department into subspecialties and anatomic regions,” Levine said. “He was way ahead of his time.”

Specialty clinics for treating groups of patients with similar problems followed.

Sculco said this change at HSS mainly influenced what happened nationally and started the trend toward subspecialization. More importantly, Wilson, Jr. created an environment where individual doctors and researchers could flourish.

The research accomplishments at HSS are as strong as its clinical areas with work underway in tendon and ligament repair, soft tissue healing, osteolysis, spine, sports medicine, cartilage repair, osteoarthritis and other areas. The hospital has a strong commitment to registries and has several, including a prospective total joint replacement registry with data on nearly 13,000 patients and one containing more than 20,000 retrieved implants.

Workers at the HSS brace shop are shown working in the early 1900s. Bracing was a large component of treatments at the hospital. More recently, orthopedic implants were fabricated on-site at the hospital.

Retrieval program

Timothy Wright, PhD, Director of the Department of Biomechanics started the HSS retrieval program in 1977 with Burstein.

The research and biomechanics programs Walker had in place when Wright joined HSS in 1976 were unmatched in the world. About then, they started collaborating with the engineering department at Cornell University’s main campus, which provided valuable resources for computer modeling, biomechanical studies and related research, Wright said.

“That collaboration has been really vital and continues today,” he told Orthopedics Today.

Collaboration

Internal collaboration between surgeons like Ranawat, Insall and Allan E. Inglis, MD, also spawned many successful concepts.

“If you look at modern total knee replacements some 30 years later, about half the market consists of posterior stabilized knees. Insall and Burstein developed that concept originally. That was a big stepping stone because it took an implant that did all the right things — it resurfaced bone so the pain went away and was well-fixed — and assured patients of something close to normal function and a larger range of motion,” Wright said, noting that nothing remotely like it was being done elsewhere.

Translational research

Another HSS achievement: digitizing radiographs and CT scans so they could be stored on computers and manipulated. “We were at the forefront of computer-aided design of implants,” Wright said.

Currently, HSS biomechanics researchers are investigating areas including tissue engineering and bone adaptation that will no doubt impact the orthopedic therapies of the future. Wright said researchers at HSS thrive because they can focus solely on the musculoskeletal system.

“It is a wonderful environment to do translational research that exists to go not just from bench top to bed, but more importantly, from bed to bench top and then back to the bed,” he said.

HSS made its name early on by treating children for scoliosis and other deformities, which was a common reason for the establishment of many orthopedic hospitals.

On the field

HSS boasts an early sports medicine specialty practice started by John Marshall, MD, which Warren, surgeon-in-chief emeritus, greatly expanded. HSS physicians are team physicians or associate team physicians for six major New York-area professional sports teams.

“I have valued the published results and teachings of John Marshall. He impacted sports medicine by making it more of an academic discipline,” Jackson said.

In terms of academics, HSS has 40 residents and a large multi-national orthopedic fellowship program, with at least one fellow working with each service and multiple fellows working with the larger ones.

“Our fellowship program has been very successful. It spawns research and interaction between our faculty, fellows and researchers which generates research studies,” Sculco said.

For more information:
Douglas W. Jackson, MD, can be reached at Memorial Orthopedic. Surgical Group, 2760 Atlantic Ave., Long Beach, CA 90806; 562-424-6666; e-mail: jacksondw@aol.com.
David B. Levine, MD, can be reached at HSS, 535 E. 70th St., New York, NY 10021; 212-606-1555; e-mail: LevineDB@hss.edu.
Thomas P. Sculco, MD, can be reached at HSS, Belaire Building, 2nd Floor, 525 East 71st St., New York, NY 10021; 212-606-1475; e-mail: sculcot@hss.edu.
Timothy Wright, PhD, can be reached at HSS, Caspary Research Building, 541 East 71st St., New York, NY 10021, 212-606-1093; e-mail: wrightt@hss.edu.

Consider femoral morphology, bone quality in selecting patients for hip resurfacing

2009-08-25T08:26:00.000-07:00

Patients who seek hip resurfacing want to lead an active lifestyle without limitations, surgeon says.

By Gina Brockenbrough
ORTHOPEDICS TODAY 2009; 29:10

The indications for total hip resurfacing are narrow, and careful patient selection and surgical technique are crucial to obtaining good outcomes.

At Orthopedics Today Hawaii 2009, Section Chair Thomas P. Schmalzried, MD, discussed the indications for hip resurfacing and presented tips on performing the procedure.

“The indications have been refined,” Schmalzried said. “There is no need for any new comer to repeat the learning curve. The patients have higher activity and break the no-restriction policy, and are at actually higher survivorship than total hip in the at-risk patient.”

Indications

The results of the procedure are due to the quality of the starting material, he said. If the walls of the acetabular component are less than 4 mm thick, the amount of acetabular reaming is similar to that for a conventional total hip component, and the operation is conservative on the acetabular and femoral side.

“There are differences on the femoral side,” Schmalzried said. “The offset of the femur after resurfacing surgery is just like it was before. You cannot change the offset. You cannot improve the offset.”

He also noted that the procedure can lengthen limbs up to 1 cm.

He has narrower indications for resurfacing than total hip replacement (THR). “My indications are those patients who are at an increased risk for failure with a total hip, [have a] good proximal femur or a femoral deformity or device that would complicate or difficult putting a total hip in,” Schmalzried said.

Thomas P. Schmalzried, MD, discussed the indications for hip resurfacing and presented tips on performing the procedure at the Orthopedics Today Hawaii 2009 meeting.

Image: Beadling L, Orthopedics Today

Patient selection

He cited research by Harlan C. Amstutz, MD, which reported a higher risk of femoral-side failure after metal-on-metal surface replacement in women, patients with smaller component sizes, large femoral defects, relative varus positioning and older patients. Large men with osteoarthritis had the highest survivorship rates, because they had denser bone and larger areas of fixation, Schmalzried said.

He said surgeons should consider resurfacing because patients are living longer and harder.

“In the eyes of many of our patients, it is not longevity,” Schmalzried said. “It is lifestyle. They are unaccepting of disability. They seek early intervention and they do not want any restrictions. They are actually more concerned about having the big spike put in their femur than the resection of the head.”

THR limits

Some surgeons emphasize the limitations of THR, making resurfacing an even more attractive option for patients.

“To some degree, the medical community has created a poor image for total hips,” Schmalzried said.

Recent studies have also indicated that resurfacing maintains bone, and that patients have better outcomes with earlier intervention. Schmalzried attributed the good outcomes of resurfacing to the patients.

“The resurfacing patients are, on average, more active than total hip replacement patients,” he said. “There are at least three studies that have seen that.” He also highlighted differences between the attitudes of patients undergoing resurfacing and THR. “The patients seek resurfacing because they intend to have a vigorous lifestyle and not accept any limitations,” Schmalzried said.

Tips

Schmalzried obtains AP, frog lateral and Johnston lateral views to perform the procedure.

“You are really resurfacing around the neck,” Schmalzried said. “You are not really resurfacing the head, so you want to make sure that you understand what is going on at the head-neck junction and translate those landmarks on the radiograph into your operation. Do not get this confused with small incision surgery. When you are first starting to do this, make a reasonable skin incision.” In addition, surgeons should avoid high lateral open angles and increased anteversion.

He uses femoral suction to get a dry interface for the cement. “Retrieval studies have indicated that aberrations in cementing are a consistent finding in short-term failures,” Schmalzried said.

Surgeons can also convert the procedure to a total hip if there is a femoral-side failure.

“In terms of operative time and blood loss, it is very similar to the primary total hip,” he said.

For more information:
Thomas P. Schmalzried, MD, medical director, Joint Replacement Institute, can be reached at 2200 W. Third St., Los Angeles, CA 90057, 213-484-7600; e-mail: schmalzried@earthlink.net He has a consulting and research relationship with DePuy, a Johnson & Johnson company, and Stryker Corp.

Reference:

Schmalzried TP. Update on total hip resurfacing. Presented at Orthopedics Today Hawaii 2009. Jan. 11-14, 2009. Kohala Coast, Hawaii.

Hip and back fractures increase mortality rates in people older than 50 years

2009-08-25T08:21:00.000-07:00

1^st on the web (August 6, 2009)

Vertebral and hip fractures are associated with an increased mortality rate in individuals over the age of 50, according to a study published this week in the Canadian Medical Association Journal.

According to the 5-year study, approximately 25% of people who develop a hip fracture and 16% who develop a spine fracture past the age of 50 will die within 5 years, according to a press release.

The research was part of the Canadian Multicentre Osteoporosis Study and consisted of 2,187 men and 5,566 women. It differs from previous studies in that the group of participants involved was representative of the general population, researchers said in the press release. Individuals were recruited via telephone lists based on postal code areas.

“Hip fractures may have long-lasting effects that result in eventual death by signaling or actually inducing a progressive decline in health,” co-investigator George Ioannidis, PhD, wrote in the study. “Our results also showed that vertebral fracture was an independent predictor of death.”

The authors concluded that interventions such as osteoporosis medications, fall prevention strategies, hip protectors and enhanced rehabilitation after fracture must be introduced to improve mobility and strength.

In a related commentary, Maureen C. Ashe, PhD, BScPT, wrote that cognitive impairment and dementia are major risk factors for fractures, but patients with these conditions are often difficult to recruit and are thus underrepresented.

“If this was the case in this Canadian cohort (and it most likely was), the mortality data may contain ‘healthy volunteer bias’ and the population mortality rates may even be higher than reported by Ioannidis and his colleagues,” she wrote.

For more information:
George Ioannidis, PhD, is a health research methodologist with McMaster University in Hamilton, Ontario. He can be reached at 501-25 Charlton Ave. East, Hamilton, ON L8N 1Y2; e-mail: g.ioannidis@sympatico.ca.

Reference:
Ioannidis G, Papaioannou A, Hopman WM, et al. Relation between fractures and mortality: Results from the Canadian Multicentre Osteoporosis Study. Can Med Assoc J. Aug. 4, 2009. DOI:10.1503/cmaj.081720

Purified stem cell group shows greater levels of Type II collagen

2009-08-25T08:16:00.000-07:00

By Gina Brockenbrough
1^st on the web (May 29, 2009)

MIAMI — Subpopulations of human mesenchymal stem cells (MSCs) may have varying potential for chondrogenic expression, according to a study presented here.

To determine if a purified subpopulation of MSCs would lead to a more uniform differentiation of cells into chondrocytes, Charles C. Secretan, MD, and his colleagues investigated the CD44 cell surface receptor which is believed to play a role in cartilage matrix generation and homoeostasis.

They reported their findings at the 8th World Congress of the International Cartilage Repair Society, here.

After culturing and isolating MSCs, the investigators used flow cytometry to detect the surface antigens in the population. They then created the following three groups of cells using a fluorescence-activated cell sorter:

a CD44-positive population;
a CD44-negative population; and,
a mixed or native population.

They used real-time polymerase chain reaction to quantify and compare the Type I collagen, Type II collagen and aggrecan content in the stem cell-derived chondrocytes in each group.

The investigators discovered significantly greater Type II collagen expression in the CD44-positive population compared to the mixed and CD44-negative groups. The CD44-positive group also showed significantly greater aggrecan expression than the mixed population.

However, the investigators found no significant difference in the aggrecan expression between the CD44-positive and negative groups. All of the groups showed high levels of Type I collagen, Secretan said.

“Human MSC populations isolated from the bone marrow [are] heterogeneous,” he said during his presentation. “There does appear to be subpopulations in human mesenchymal stem cells with functional and differential capabilities, and a CD44 purified mesenchymal stem cell population did show an enhanced ability to produce more Type II collagen and aggrecan [compared to a mixed population].”

Reference:
Secretan CC, Bater J, Bagnall KN, et al. Isolation of a subpopulation of human mesenchymal stem cells with enhanced chondrogenic potential. #9.2.5. Presented at the 8th World Congress of the International Cartilage Repair Society. May 23-26, 2009. Miami.

Scientists closer to making implantable bone material for orthopedics

2009-08-25T08:15:00.001-07:00

1^st on the web (July 28, 2009)

Researchers are closer to understanding how to grow replacement bones using stem cell technology, according to research published Sunday in the journal Nature Materials.

Scientists from Imperial College London compared the bone-like material grown from three different, commonly used, clinically relevant cell types and discovered significant differences between the qualities of bone-like material that these can form, according to a press release.

Among these discoveries: Bone-like materials that were grown from bone cells in mouse skull and mouse bone marrow stem cells successfully mimicked many of the hallmarks of real bone, including stiffness. The investigators also found that the bone-like material grown from mouse embryonic stem cells was much less stiff and complex in its mineral composition when compared to the other materials.

The scientists suggest that further research is now needed to explore the implications of these results for different stem cell therapies.

Researchers used laser-based Raman spectroscopy and multivariate statistical analysis techniques, which enabled them to compare and analyze data about the growth of different cell populations and understand the detailed chemical make-up of live cells as they grew. They also used a nano-indenter and high resolution electron microscopy, which allowed them to probe the samples so they could understand how stiff the bone-like materials were and what their structure was at a microscopic level.

“Our study provides an important insight into how different cell sources can really influence the quality of bone that we can produce,” Molly Stevens, a professor with the Institute of Biomedical Engineering at Imperial College London, said in the press release. “It brings us one step closer to developing materials that will have the highest chance of success when implanted into patients.”

Reference:
Gentleman E, Swain RJ, Evans ND, et al. Comparative materials differences revealed in engineered bone as a function of cell-specific differentiation. Nat Mater. July 26, 2009.

For more information:
www.imperial.ac.uk

NY surgeon survives lightning strike and discovers a surprising musical ability

2009-08-25T08:13:00.000-07:00

Anthony D. Cicoria, MD, has gained notoriety from his near-death experience and music-filled dreams.

By Susan M Rapp
ORTHOPEDICS TODAY 2009; 29:52

The first CD of music written and performed by orthopedic surgeon Anthony D. Cicoria, MD, a novice piano composer, contains 27 minutes and 44 seconds of haunting themes, pensive melodies, sudden crescendos and peaceful interludes that should appeal to many listeners.

However, most will likely listen a little closer to this CD released last year once they learn Cicoria did not get to where he is today musically, which includes playing sold-out concerts, by practicing or studying composition.

Cicoria became a pianist and composer by accident.

Near-death experience

In 1994 Cicoria was struck by lightning and suffered cardiac arrest. The way he tells it, he briefly died, saw himself dead on the ground in an out-of-body experience and, for some unknown reason he is still grappling with, lived to tell his amazing story.

With this new “life” came an implausible change in a man who worked 10- to 12-hour-days as the only orthopedist in Chenango County, N.Y., and enjoyed life raising his three children, but had little time for much else.

“It was just a few weeks afterwards when I started to have a craving to hear classical piano music,” Cicoria told Orthopedics Today.

The craving was so strong he felt compelled to drive nearly an hour to the closest large music store and purchase a CD of Chopin piano music. He soon acquired a piano.

“And that’s how it all started,” according to Cicoria.

Cicoria is the only orthopedist in his county. He must fit his piano practicing, composing and performances into his busy surgical and office schedule.

Images: Cicoria AD

Music in dreams

Cicoria eventually learned to play the piano studying on his own and later starting lessons in 1998 with Sandra McKane, who was trained at the Julliard School.

After the accident, pieces of complex music started coming to him in dreams or emerged when he was playing other composer’s works, haunting him until he could get them notated, which he did with special computer software and help from McKane and others.

Now when Cicoria writes, “The music comes and unfolds,” he said.

Publicized case

Cicoria admitted that dealing with this new musical component of his life over the past 15 years has not been easy, especially at first.

“Somehow, I had deluded myself into thinking the only reason I had survived had something to do with this music. I really became a bit of a fanatic about it,” he said.

Cicoria connected in 2006 with world-famous neurologist Oliver Sacks, MD, FRCP, who helped him gain insight into the possible causes of his unusual new musical abilities. After that meeting, Cicoria’s story was widely covered by the media, including a BBC television feature and a piece by Sacks published in The New Yorker in 2007.

Cicoria has since heard from others who underwent equally unusual experiences and from some who claim his music healed their chronic pain or affected them in other positive ways.

Wake-up call

Fortunately, there were few physical sequelae from the lightning strike.

“I had a burn on my face where [the lightning bolt] went in and on my foot where it came out, so I had gotten hit pretty hard. Although for a week afterwards I was pretty fuzzy, it eventually cleared,” he said.

Immediately following the lightning strike, “I was not sure what it all meant other than the fact it was kind of a wake-up call.”

Tests showed no changes to Cicoria’s brain that might account for his new-found music ability, however Sacks developed theories about what happened. “He thinks there had to have been some rewiring of my brain because I had a presumed cardiac arrest,” Cicoria said.

After surviving a lightning strike, Anthony D. Cicoria, MD, suddenly wanted to play the piano and started composing music. He now urges his children and others to follow their passions in life because they will always lead to happiness.

Musical gene

Before 1994, Cicoria’s musical interest pretty much consisted of listening to rock and roll. “There was not much of anything else,” he said. His formal music training included a year of piano lessons when he was 7 years old which he disliked.

“There must be some sort of a music gene in the family. One of Dr. Sacks’ speculations is this gene was there in the brain and the lightning has allowed it to be expressed,” Cicoria said.

Before all the publicity emerged, Cicoria said he was reticent about discussing his experiences. “It almost sounds a little bit on the fringe of reality. It is not exactly the kind of thing you want to portray as a physician and surgeon.”

“Until Sacks took it out of the closet, it was my private little story and my private quest for music. All of a sudden it was everywhere. Perhaps it was supposed to be that way. That is why I have got to laugh and say it has taken on a life of its own, because had it been left up to me it would still be in the drawer. It would be between me and my muse, whatever that is.”

With more concerts scheduled and a symphony, two concertos and other pieces in the works, Cicoria is far from locking his talents away. He hopes to eventually transition to where music is the centerpiece of his life, but “I also do not see myself just quitting orthopedics either. It will be an interesting next 5 to 10 years.”

For more information:
Anthony D. Cicoria, MD, can be reached at P.O. Box 271, Norwich, NY 13815; 607-337-4700; e-mail: tcicoria@yahoo.com.

References:

http://cdbaby.com/cd/drtonycicoria
Sacks O. A neurologist’s notebook: A bolt from the blue: Where do sudden passions come from? The New Yorker. 2007; Jul 23:38-42.

Hyaline-like tissue seen in defects treated with stem cells and platelet rich plasma

2009-08-25T08:12:00.001-07:00

Analysis showed a higher relation between Collagen I and II after stem cell treatments.

By Gina Brockenbrough
ORTHOPEDICS TODAY 2009; 29:28

MIAMI — Treating chondral defects with mesenchymal stem cells delivered in a scaffold with platelet-rich plasma may result in repair tissue with properties more similar to normal hyaline cartilage than the repair tissue seen in controls, the use of scaffolds alone or loading scaffolds with stem cells alone.

“The treatment of full-thickness chondral defects with a collagen scaffold, mesenchymal stem cells compromised to the chondrocyte lineage and platelet rich plasma shows promising results,” Alex Vaisman, MD, said during his presentation at the 8th World Congress of the International Cartilage Repair Society. “Nevertheless, none of the treatment groups healed with normal hyaline cartilage.”

To evaluate the properties of repair tissue created after treating full-thickness chondral defects of the knee with a bi-layer collagen scaffold embedded with autologous mesenchymal stem cells (MSCs) induced to chondrocyte differentiation and platelet-rich plasma (PRP), Vaisman and his colleagues created 20 mm² acute full-thickness chondral defects in 36 femoral condyles of adult male New Zealand White rabbits.

They randomly assigned the rabbits to the following four groups:

Group 1 in which the lesion was left untreated;
Group 2 in which surgeons implanted a scaffold without MSCs or PRP;
Group 3 in which a scaffold containing MSCs was implanted; and
Group 4 in which a scaffold contained MSCs and PRP.

The investigators sacrificed the rabbits after 6 months. They evaluated the femoral condyles macroscopically, histologically using hematoxylin-eosin and Toluidine Blue staining, and molecularly using quantitative real-time polymerase chain reaction of Collagen II/I and aggrecan/versican.

Evaluation

A rabbit knee with a scaffold containing mesenchymal stem cells and platelet-rich plasma.

Image: Vaisman A

Using macroscopy, the investigators discovered fibrous tissue without bony exposure in the control group.

“Groups 2 and 3 showed a hypertrophic, soft, irregular tissue covering the whole lesion,” Vaisman said. “Group 4 has similar- to normal-hyaline cartilage.”

Histology revealed that all of the groups had some fibrocartilage, but the investigators found no significant difference among the groups.

“However, groups 3 and 4 had a slightly more similar appearance to hyaline cartilage than the other groups,” Vaisman said.

Upon molecular analysis, the investigators discovered that groups 3 and 4 had a significantly higher relation between Collagen II and I compared to the other groups.

Alan J. Nixon, MD, a co-moderator of the session, noted that PRP can contain a variety of growth factors. “Do you know what you used for PRP?” Nixon asked. “Did you assay what factors were in that?”

Vaisman said that the investigators did not assess which growth factors were in the PRP or determine the concentrations of these growth factors.

For more information:
Alan J. Nixon, MD, can be reached at Cornell University, College of Veterinary Medicine, C3-187 VMC, Ithaca, NY 14853; 607-253-3224; e-mail: ajn1@cornell.edu.
Alex Vaisman, MD, can be reached at Orthopaedic Surgery Unit, Clínica Alemana de Santiago, and Faculty of Medicine, Universidad del Desarrollo, P.O. Box 3737, Santiago, Chile; (56-2) 210-11 11, 212-97 00; e-mail: avaisman@alemana.cl. They have no direct financial interest in any companies or products mentioned in this article.

Reference:

Vaisman A, Figueroa D, Calvo R, et al. Treatment of full-thickness chondral defects with a collagen scaffold, mesenchymal stem cells compromised to the chondrocyte lineage and platelet rich plasma. Paper #9.2.7. Presented at the 8th World Congress of the International Cartilage Repair Society. May 23-26, 2009. Miami.

Navigation-assisted bone tumor surgery may lead to better resection, function

2009-08-25T08:10:00.001-07:00

Investigators from Korea found a mean registration error of less than 1 mm with navigation surgery.

By Gina Brockenbrough
ORTHOPEDICS TODAY 2009; 29:35

Performing bone tumor resection using a navigation system can improve the accuracy of the surgical resection and help preserve limb function, according to researchers from Korea.

“Under navigated guidance, three-dimensional anatomy of the tumor and the surrounding normal tissue can be visualized during surgery,” Hwan-Seong Cho, MD, said during his presentation at the American Academy of Orthopaedic Surgeons annual meeting. “Precise control of the resection margin is possible, enabling us to achieve the resection margin determined preoperatively. In selected patients, this technique can be helpful in increasing the accuracy of surgical resection and in reducing the functional impairment.”

Malignant bone tumors

Cho and his colleagues studied patients with a total of 11 primary bone tumors or solitary bone metastases who underwent bone tumor resection and joint preservation limb surgery using a navigation system at Seoul National University College of Medicine since 2005. Preoperatively, the patients had malignant fibrous histiocytoma of bone, high-grade chondrosarcomas, Ewing’s sarcomas, osteosarcomas, and solitary bone metastases from rectal or thyroid cancers.

Surgeons used a navigation system during four internal hemipelvectomies, two partial sacrotomies and five joint preserving limb salvage procedures. They performed joint preserving limb surgery if the following conditions were met:

A T2-weighted spin-echo axial image shows a lobulated lesion with a high signal intensity confined to right sacral ala.

Images: Cho HS

the tumor was located in the metaphyseal region;
the preoperative chemotherapy was estimated to be effective as evidenced by imaging studies; and
the remaining epiphysis was expected to be more than 1 cm long after tumor resection with a 1 cm- to 2 cm-surgical margin.

The navigation system took a mean time of almost 51 minutes to set-up, and the investigators followed the patients for a mean of 18.5 months.

Accuracy

The investigators discovered that the mean registration error was less than 1 mm.

“The distances from the tumor to the resection margins on the pathologic examination were in accordance with those of the preoperative plans,” Cho said. The patients had a mean Musculoskeletal Tumor Society functional score of 28 points, and the investigators found no cases of local recurrence at the latest follow-up.

Soft tissues, blood loss

During the paper discussion, audience member Lawrence R. Menendez, MD, asked if the investigators used navigation to measure the surgical margins during the soft tissue resection.

“I used the navigation system for only the osteotomy,” Cho said. “For the soft tissue resection, I use conventional methods.”

Menendez noted that navigation has been used for soft tissue procedures in other fields such as neurosurgery.

Cho replied, “But, in the soft tissue sarcoma, we cannot technically attach the dynamic reference base.”

Another audience member asked if the investigators noticed a difference in blood loss during tumor resection when using navigation.

“I did not compare the blood loss between the conventional method and the navigation use, but I guess that there is no big difference,” Cho said.

A dynamic reference-base was fixed to the spinous process of L5. Tumor resection with wide margin was performed under navigation guidance.

The tumor was excised with an adequate surgical margin as planned and L5 nerve root and sacral nerve roots could be preserved.

For more information:
Hwan-Seong Cho, MD, can be reached at Kyungpook National University College of Medicine, 200 Dongduk-ro Jung-gu, Daegu, 700-721, South Korea; 82-53-420-6322; e-mail: mdchs111@snu.ac.kr. He receives research or institutional support from Aesculap/B. Braun and Smith & Nephew.
Lawrence R. Menendez, MD, is the Director of Orthopaedic Oncology at the University of Southern California University Hospital. He can be reached at 1520 San Pablo St., Suit e 2000, Los Angeles, CA 90033; 323-442-5830; e-mail: menendez@usc.edu. Neither source has any financial interest in any products or companies mentioned in this article.

Reference:

Cho HS, Han I, Oh JH, et al. Bone tumor resection under navigation guidance. Paper #469. Presented at the American Academy of Orthopaedic Surgeons 76th Annual Meeting. February 25-28, 2009. Las Vegas.
Cho HS, Kang HG, Kim HS, Han I. Computer-assisted sacral tumor resection. A case report. J Bone Joint Surg (Am). 2008;90(7):1561-1566.
Cho HS, Oh JH, Han I, Kim HS. Joint-preserving limb salvage surgery under navigation guidance. J Surg Oncol. 2009 Mar 27. [Epub ahead of print]

Doctor traveling with fellows quarantined 7 days in Hong Kong after H1N1 exposure

2009-08-25T08:09:00.000-07:00

He spent 2 days on a hospital infectious disease ward and then was confined to a camp.

By Susan M Rapp
ORTHOPEDICS TODAY 2009; 29:24

At the height of recent worldwide concern over the spread of influenza A, H1N1, a U.S. orthopedic surgeon was quarantined in a hospital and camp in Hong Kong for 7 days after a passenger on his overseas flight developed H1N1, or swine flu.

One day after arriving in Hong Kong, health authorities contacted Alvin H. Crawford, MD, FACS, an Orthopedics Today Editorial Board section editor, to alert him a situation was developing related to a sick passenger on his flight.

Extra caution

“The Asian countries are in sort of a heightened state of alert because of their previous experience with SARS,” he told Orthopedics Today after returning from his trip.

Crawford was traveling to Asia to mentor three spine surgeons considered to be the best and brightest of the Scoliosis Research Society (SRS) candidate members. They were participating in the SRS Traveling Fellowship Program, a trip that included stops in Hong Kong, Beijing, Tokyo, Singapore and Seoul.

Orthopedics Today Editorial Board Section Editor Alvin H. Crawford, MD, was required to wear a surgical mask and identification badge at all times when quarantined in a Hong Kong camp due to a swine flu scare. He is pictured here after his daily physical examination and Tamiflu shot.

Images: Crawford AH

Part of his journey involved a Detroit-to-Tokyo flight, prior to landing in Hong Kong.

“I was made aware in Hong Kong there was a passenger on the flight from Detroit to Tokyo who had come down with swine flu,” Crawford said.

They told him the three-row rule was in effect and he was not seated within three rows of the ill person. He then lectured at the Chinese University and had taken an excursion and came in contact with many people.

Crawford felt his risk of contracting or spreading H1N1 was low, but later Hong Kong health authorities told him a passenger sitting in front of him also developed H1N1.

Although he did not have a fever or other symptoms, the Hong Kong authorities made him aware that he would have to undergo an examination and testing, he said. He was taken to Princess Margaret Hospital and kept in isolation on the infectious disease ward for 2 days under observation, undergoing testing and starting a course of Tamiflu (oseltamivir phosphate, Roche). All of Crawford’s tests came back negative; however, that was not the resolution of the issue. He was confined and his young traveling companions continued on their trip to Beijing without him.

Quarantine camp

He was then transferred to a camp near the mainland China border for the remainder of his quarantine, where he was assigned a bungalow, was required to wear a mask, picked up his meals at a canteen, and was observed to ensure he took his flu medication daily. Socialization with others quarantined at the camp was discouraged.

He spent his time there cruising the Internet, reading everything he could find and practicing the clarinet.

Crawford contacted the U.S. State Department and a colleague in Hong Kong — a friend of the Minister of Health — for assistance, but those efforts failed to shorten his quarantine time.

Upon release 5 days later, he received a certificate stating he had been quarantined and treated for H1N1, but even with that Crawford was concerned he might get stopped when he flew to Japan to connect with the traveling fellows because 10-day quarantines were in effect there. His choices were to risk further quarantine in Japan, if another passenger came down with the flu, or head back to Cincinnati.

“I elected to re-join the group,” he said. “I went to Tokyo and met up with the group and encountered no further problems,” Crawford said.

The traveling fellows told him one hospital they were scheduled to visit in Beijing and another in Hong Kong were closed to foreign visitors due to the H1N1 situation.

Crawford, who ran a hospital orthopedic department for 28 years, feels he probably has a greater appreciation for how these kinds of administrative issues impact the practice of medicine.

Part of the 7-day quarantine for H1N1 exposure included time at a camp on Hong Kong’s border near mainland China. Workers are shown here between performing exams and giving Tamiflu shots to detainees.

“I knew there was possibly little risk in terms of contamination, but realized it was a government decision made on a bureaucratic level. Once you mentally process and resolve that, it becomes a little easier,” he said. “The H1N1 story is by no means over and its worldwide impact has yet to be determined.”

Crawford’s chief concern during his ordeal remained his responsibility to mentor the fellows and introduce them to key people at each stop of the trip.

“Fortunately, only one leg of the trip was interrupted.”

For more information:
Alvin H. Crawford, MD, can be reached at Cincinnati Children’s Hospital Medical Center, Division of Pediatric Orthopaedic Surgery, 3333 Burnet Ave., Building C, MLC #2017, Cincinnati, OH 45229-3026; 513-636-4787; e-mail: alvin.crawford@cchmc.org.

Students embed stem cells in sutures to enhance healing

2009-08-25T08:08:00.000-07:00

1^st on the web (August 10, 2009)

Johns Hopkins biomedical engineering students have demonstrated a practical way to embed a patient's own adult stem cells in the surgical thread that doctors use to repair serious orthopedic injuries such as ruptured tendons.

The students’ goal is to enhance healing and reduce the likelihood of re-injury without changing the surgical procedure itself.

The project team – 10 undergraduates sponsored by Bioactive Surgical Inc. – won first place in the recent Design Day 2009 competition conducted by the university's Department of Biomedical Engineering. In collaboration with orthopedic physicians, the students have begun testing the stem cell–bearing sutures in an animal model, paving the way for possible human trials within about five years.

"Using sutures that carry stems cells to the injury site would not change the way surgeons repair the injury," said Matt Rubashkin, the student team leader, in a release. “We believe the stem cells will significantly speed up and improve the healing process. And because the stem cells will come from the patient, there should be no rejection problems."

The corporate sponsor, Bioactive Surgical, developed the patent-pending concept for a new way to embed stem cells in sutures during the surgical process. The company then enlisted the student team to assemble and test a prototype to demonstrate that the concept was sound. The undergraduates performed this work during the yearlong Design Team course, required by the school's Biomedical Engineering Department.

As envisioned by the company and the students, a doctor would withdraw bone marrow containing stem cells from a patient's hip while the patient was under anesthesia. The stem cells would then be embedded in the novel suture through a quick and easily performed proprietary process. The surgeon would then stitch together the ruptured Achilles tendon or other injury in the conventional manner but using the sutures embedded with stem cells.

At the site of the injury, the stem cells are expected to reduce inflammation and release growth factor proteins that speed up the healing, enhancing the prospects for a full recovery and reducing the likelihood of re-injury. The team's preliminary experiments in an animal model have yielded promising results, indicating that the stem cells attached to the sutures can survive the surgical process and retain the ability to turn into replacement tissue, such as tendon or cartilage.

"These students have demonstrated an amazing amount of initiative and leadership in all aspects of this project, including actually producing the suture and designing the ensuing mechanical, cell-based and animal trials," said Lew C. Schon, MD, one of the inventors of the technology, in a release. “The students exceeded all expectations. They have probably cut at least a year off of the development time of this technology, and they are definitely advancing the science in this emerging area.”

For more information:
Lew C. Schon, MD, is an assistant professor of orthopedic surgery in the Johns Hopkins School of Medicine. He can be reached at 3333 N. Calvert Street Johnston Prof. Building, Suite 400 Baltimore, MD 21218; (800)-571-9820; e-mail: lschon@gcoa.net.

Tendon reconstruction is recommended for treating ankle instability

2009-08-25T08:04:00.001-07:00

Long-term problems, multiple re-injuries may impede ligament reconstructions.

By Nicholas A. Abidi, MD
ORTHOPEDICS TODAY 2008; 28:88

Ankle instability is probably one of the most common sports injuries that we see each day in the United States: some 27,000 per day. It was the most common reason for a trip to the emergency room at one point and typically it is an inversion mechanism.

Nicholas A. Abidi

Overall, if it is instability and ankle sprain, what is the big deal? Our goal in nonoperative and operative treatment should be to prevent the occurrence of sprains, since they have been shown in the literature and in our practices to prevent the long-term development of arthritis in many cases.

I used to perform the Broström-Gould procedure. I had pretty good results with that in the first 5 or 6 years in practice and I am happy with that. But as I thought about long-term problems after 3 to 5 years of following these patients, I realized I could not reconstruct the ligaments effectively in many patients in the middle of surgery, and I didn’t necessarily have an alternative other than some nonanatomic tendon reconstructions.

I surveyed Canadian surgeons several years ago and they recently told me that because of the long waiting list for patients there, many of the surgeons have switched to tendon reconstruction procedures because they determined that the Broström-Gould didn’t always give good long-term results.

Many have also told me that they have to make this decision intraoperatively based on the quality of the tissue, and that they have to justify using anchors because the cost of implants or tendon grafts limits their use in their provinces.

Athletic population

I use tendon reconstruction in people who have failed bracing and are athletes. Many of them have more than 10 years of ankle instability as well as hyperextension, patellofemoral, elbow and shoulder issues. I have a highly athletic patient population, being near a military base on the West Coast, and I noticed that when I looked at the older series with the Broström-Gould technique that most patients had several reinjuries. Many patients obviously will have more reoccurring instability at 3 to 5 years, and I couldn’t explain it other than that their tissues had given up. Reconstructions were the same every time, and in the end, adding the Gould modifications didn’t make it a true anatomic reconstruction

I thought about how there are so many papers are going back to the 1960s that talk about ligament construction and how that progressed to interest in tendon reconstruction. The patients were unsatisfied with their ligament reconstructions.

There are many types of ankle ligament reconstructions, not all necessarily anatomic, and many downfalls, too. There are about 25 types of Christian-Snook procedures that cross the subtalar joint as many as three times, they were not anatomic and they were very stiff — perhaps worse than a fusion sometimes.

The Evans reconstruction that is an augmentation has been shown to create subtalar joint arthritis over the long term. The Colville procedure is not really anatomic because it keeps the peroneus brevis tendons attached and has limited inversion in some patients at long-term.

Anatomic reconstruction

Now switch to anatomic reconstruction. Coughlin and Younger are both high-volume surgeons and their papers are being published on using tendon graft with interference anchors in the heel and in the neck of the talus, where it maintains the 105° axis. The theory behind it is that the tendons are less likely to attenuate with time as much as the ligaments do.

Using anchors permits early motion. In the Broström-Gould approach, we were casting for 4 to 6 weeks, which led to its own morbidity and relied upon scar tissue in the procedures, which is sometimes relying on wishful thinking. In many cases, I found attenuation at long-term follow-up.

There are more recent anatomic ligament reconstructions. I try to avoid the ones using gracilis autograft from the knee because I think the graft is a bit bulky and requires accessing the medial knee for an ankle procedure. Nevertheless, investigators have found outstanding results in that they had one recurrence at the most in a large series of patients.

Technique

At the time I was doing the Colville procedure, I had a patient with no peroneus brevis ligament to reconstruct … only a peroneus longus and severe instability. So I took a strip of that and discovered that the length was perfect to reconstruct the ankle. The results were outstanding. I look forward to advancing the procedure by using it on other patients who I can study, using a linear incision along the course of the fibula that to see if it works as well.

I run a linear incision along the course of the fibula but above the superior retinaculum to about one-third of the peroneus longus, and remove it with a tendon stripper. I attach the graft to the origin of the calcaneofibular ligament (CFL) underneath the peroneal tendons through a tunnel in the fibula and then down to the anterior talofibular ligament (ATFL) and anchor it into the neck of the talus with an interference anchor. We then pull up the capsule, which we peeled off of the distal fibula, and suture it back to the fibula. We may supplement it with the Gould modification in high-demand patients. It is not necessarily as tight or as a solid as a primary Brostrum, but it closes the capsule and prevents impinging tissue.

Postoperative rehabilitation begins with nonweight-bearing for 2 weeks and then weight-bearing with a walker for 2 weeks, leg splints for 2 weeks and no long-term mobilization. For physical therapy, there are six to 12 physical therapy sessions.

I have entered patients who have chronic ankle instability with functional and demonstrable MRIs and variable demands into a new study. Most are of a high-performance military population on a military base, and quite a few are recreational athletes in our area. We used validated instruments prospectively with 30 patients and hope to finish collecting the data soon and validate that. So far, the SF12 scores improved in the physical and mental components.

Zero recurrance

The thing that I really noticed when I’ve talked to people who have used this procedure is that the incidence of recurrent injury in patients is flat zero. These guys are jumping over brick walls and jumping out of helicopters. The patients can swim, run marathons, participate in triathlons and return to regular full-service duty after the reconstruction, and they get back quickly.

They said that when they turned their ankle didn’t sprain, so that was a good thing. The downside seems to be numbness, which seems to go along with the Broström procedure and similar incisions as well. The worst of the patients had stiffness in the first 3 months. We mobilized them with cortisone to get them moving, and they seem to be doing pretty well in 6 months.

In summary, I found the Broström-Gould procedure sometimes to be less filling, while the anatomic tendon reconstruction to taste great. But, if you look at the overall evidence-based literature, essentially when you look at the comparison trials that were done with the older techniques and not these, there are no evidence-based comparison studies at level 2 or level 1 instances that compare these types of reconstructions, and some have to be done.

For more information:
Nicholas A. Abidi, MD, can be reached at Santa Cruz Orthopaedic Institute, 1505 Soquel Drive, Suite 12, Santa Cruz, CA 95065; 831-475-4024; e-mail: nabidi@comcast.net. He has no direct financial interest in any product or company mentioned in the article.
Reference:

Abidi NA. Tendon reconstruction. Presented as part of the Ankle Instability Debate at the 38th Annual Winter Meeting of the American Orthopaedic Foot and Ankle Society. March 8, 2008. San Francisco.

Atraumatic Bilateral Femur Fracture in Long-Term Bisphosphonate Use

2009-08-25T07:59:00.000-07:00

By Maria S. Goddard, MD; Kristoff R. Reid, MD; James C. Johnston, MD; Harpal S. Khanuja, MD
ORTHOPEDICS 2009; 32:607

Abstract

Postmenopausal women with osteoporosis are commonly treated with the bisphosphonate class of medications, one of the most frequently prescribed medications in the United States. In the past 4 years, reports have been published implying that long-term bisphosphonate therapy could be linked to atraumatic femoral diaphyseal fractures.

This article presents a case of a 67-year-old woman who presented with an atraumatic right femur fracture. She had a medical history notable for use of the bisphosphonate alendronate for 16 years before being switched to ibandronate for 1 year before presentation. She had sustained a similar fracture on the contralateral side 3 years previously.

This case report, in addition to a review of the literature, shows that use of the bisphosphonate class of medications for an extended period of time may result in an increased susceptibility to atraumatic femoral diaphyseal fractures. Some studies have suggested that the reason may be the mechanism of action of bisphosphonates, resulting in decreased bone turnover and remodeling. Studies have not shown if the entire class of medications produce a similar result, but patients who have been treated with any bisphosphonate for an extended period of time should be considered at risk. In patients who have already sustained a femoral diaphyseal fracture, imaging of the contralateral side should be performed to identify cortical thickening as an early sign of fracture risk. Patients should also be questioned about thigh pain.

Postmenopausal women with osteoporosis are commonly treated with the bisphosphonate class of medications. In 2006, approximately 22 million prescriptions for this medication were written in the United States (National Prescription Audit Plus 2006; IMS Health, Norwalk, Connecticut). However, since 2005, reports have been published indicating that long-term bisphosphonate therapy could be linked to atraumatic low-energy femoral shaft fractures.^1-7 This article presents a case of a 67-year-old woman with a history of sequential bilateral atraumatic femur fractures after long-term use of bisphosphonates.

Case Report

A 67-year-old woman presented to the emergency department with a spontaneous right femoral diaphyseal fracture. There was no history of trauma and she denied antecedent pain. A review of her medical history revealed that she had sustained a left femoral diaphyseal fracture under similar circumstances 3 years previously, which had been treated with intramedullary nailing. In that earlier injury, she reported a feeling of “giving way” before falling. She had no risk factors for pathologic fractures. She was a nonsmoker and did not take corticosteroids. She had a distant history of hormone replacement therapy before 1985 to prevent osteoporosis. She began taking alendronate 70 mg per week in 1991 for osteopenia and was switched to ibandronate 150 mg monthly in 2007 for a more convenient dosing regimen. In addition, her past medical history included degenerative thoracolumbar scoliosis.

Radiographs of the pelvis, right hip, and right femur revealed a displaced diaphyseal fracture at the proximal and middle one-third right femoral junction. There was evidence of osteopenia in the metaphyseal regions (Figure 1). Given her previous history of fracture on the contralateral side and a lack of risk factors for spontaneous fractures, a magnetic resonance imaging scan without contrast was obtained to exclude a pathologic fracture. It showed no evidence of a bone lesion or other abnormality. A review of the records from her previous fracture showed no radiographic evidence of an underlying malignancy to explain that injury.

On the day of admission, she underwent cephalomedullary rod fixation. There were no postoperative complications, and she was discharged after 5 days. Pathologic analysis of bone fragments removed during the procedure showed bony trabeculae and hyaline cartilage with no evidence of granulomas or tumors.

At 6-month follow-up, the patient reported minimal pain at the fracture site. She was ambulating with a cane and maintained full range of motion. Radiographs showed the intramedullary rod in place with evidence of callus formation and a visible fracture line (Figure 2). Because of signs of delayed union, dynamization was performed by removing the distal interlocking screw. She has elected to discontinue use of any type of bisphosphonate medication since her second fall. Conventional radiographs at 1-year follow-up showed that the fracture had healed completely (Figure 3).



Figure 1: Preoperative conventional AP radiograph showing the characteristic fracture pattern of cortical thickening and a unicortical beak. Figure 2: Postoperative conventional AP (A) and lateral (B) radiographs taken 4 months after injury, showing callus formation and visible fracture line. Figure 3: Postoperative radiograph at 1-year follow-up visit showing a completely healed fracture.

Discussion

Some studies have suggested that long-standing bisphosphonate use may be a risk factor for atraumatic femoral shaft fractures.^1-8 It is believed that bisphosphonates inhibit the normal bone remodeling cycle, thus limiting native repair and leading to the accumulation of microfractures, which places a patient at an increased risk for long-bone fractures.^8,9 In a dual-center study, Odvina et al⁸ examined the bone biopsy results from 9 patients treated with alendronate for 3 to 8 years for osteoporosis or osteopenia; those authors proposed that the mechanism behind this paradoxical increased incidence of femoral shaft fractures is severe suppression of bone turnover by bisphosphonates. They confirmed this theory histologically as a decrease in the osteoclastic and osteoblastic surfaces and identified a reduction or lack of tetracycline labeling, indicating diminished mineralized bone.⁸ All patients, including those who were given estrogen therapy, had decreased bone formation and no double-tetracycline labeling.

Because bisphosphonates bind to bone and are slowly released during bone resorption,¹⁰ it may take several years for any detrimental effect to become evident. For example, alendronate has a half-life of 10.9 years,¹¹ and therefore could be present in the body long after therapy is stopped. One study has shown that, after taking alendronate for 5 years, the biochemical markers of bone turnover remained suppressed for at least 3 years after its discontinuation.¹² Using a pharmacokinetic model with a dose of 10 mg per day, Rodan et al¹³ found that the amount of alendronate retained in bone after 10 years of treatment was approximately 75 mg per 2 kg of mineral.

Our patient, who sustained sequential bilateral femoral diaphyseal fractures within a 3-year period, had been treated with bisphosphonates (alendronate and ibandronate) for osteopenia for more than 16 years. Given similar mechanisms without substantial trauma and no other risk factors for these fractures, the long-term use of bisphosphonates is implicated.

Alendronate has been the bisphosphonate most commonly used and has been implicated in most of the reported cases of atraumatic femur fractures. It is likely a class effect, that is, an effect related to bisphosphonates in general rather than to a specific medication. It is likely that other bisphosphonates will result in more complications as their use increases. Using a rat model, Yang et al¹⁴ showed that high levels of the bisphosphonate pamidronate lowered the bone mineral density and mechanical strength of the femur. In addition, they also found that there was reduced healing and callus formation after fracture in femurs with a high intraosseous concentration of pamidronate. They suggested that severe suppression of bone turnover also occurs with bisphosphonates other than alendronate, in high concentrations and over time.

Ott¹⁵ recommended that treatment with bisphosphonates be stopped after 5 years and that patients that require additional fracture protection be given parathyroid hormone. The rationale for this timeframe is to allow adequate time for fracture prevention while minimizing the risks of severe suppression bone turnover. A more recent study by Sebba¹⁶ suggested a medication holiday of 1 year to reduce the fracture risk from long-term uninterrupted use because there is no reduction of the protective benefit during that time. Some studies have shown that discontinuation of alendronate after this time period does not diminish the protective effect for vertebral fractures.¹⁰ It is important to define the minimal duration of treatment needed for osteoporosis to reduce the side effects of these medications.

One study has shown that treatment with estrogen replacement in combination with bisphosphonates resulted in greater levels of suppression of bone turnover than use of the latter alone.¹⁷ Although our patient had a distant history of estrogen use, it was not concomitant with her bisphosphonate therapy.

Atraumatic femoral diaphyseal fractures occurring in long-term bisphosphonate use have similar characteristics: a simple transverse pattern, unicortical beak, and cortical hypertrophy.^3-6 The fracture pattern in our patient was similar to that described in other studies^3-6; it appears to be pathognomonic for a femoral fracture in long-term bisphosphonate use. In a case series of 17 patients on alendronate therapy with subtrochanteric insufficiency fractures, Kwek et al³ found that all patients experienced prodromal pain and that all had similar radiographic fracture patterns. These patterns included a transverse fracture with lateral pattern, which they described as simple with thick cortices. In a 5-year retrospective review of 70 patients with low-energy femoral fractures, Neviaser et al⁵ found that of 25 patients being treated with alendronate, 19 (76%) had a simple, transverse fracture with a unicortical beak in an area of cortical hypertrophy. Only 1 patient of the remaining 45 who were not treated with alendronate in this study had these radiographic findings.

To our knowledge, a bilateral fracture in association with bisphosphonate use over an extended period of time has been reported in only 1 other case.¹ In that study, Cheung et al¹ showed suppressed bone turnover in their patient by using a double-tetracycline-labeled bone biopsy of the anterior superior iliac spine. Goh et al² examined 9 patients who sustained subtrochanteric insufficiency fractures while on alendronate and found hypertrophy of the cortex on the contralateral side in 3 patients, implying a risk for bilateral fracture development.

Since our patient’s follow-up, we have identified 2 other patients with atraumatic fractures after bisphosphonate therapy for several years, 1 of whom had evidence of a cortical stress reaction on the opposite side. For patients presenting with a low-energy subtrochanteric or diaphyseal femur fracture and a history of long-term bisphosphonate treatment, we recommend that such medications be considered a part of the underlying abnormality. Attention should also be paid to patients who have been treated with bisphosphonates for a long time who report thigh pain because this symptom might be an early indication of an impending fracture. We also recommend that patients on bisphosphonate therapy who have already had a femoral fracture should undergo one-time imaging of the contralateral side to identify any cortical thickening. If thickening is identified, consideration should be given to a medication holiday or termination of the bisphosphonate therapy. This decision should be made in conjunction with the physician who prescribed the medication.

It seems clear that in certain patients, chronic use of bisphosphonates predisposes them to low-energy or atraumatic long bone fractures. Undoubtedly, these medications are beneficial for the prevention of vertebral compression and other osteoporotic fractures,^18,19 and the discontinuation of bisphosphonates should be discussed with the patient’s primary physician. Additional pathophysiology studies are needed to identify patients who are at risk for this major complication.

References

Cheung RKH, Leung KK, Lee KC, Chow TC. Sequential non-traumatic femoral shaft fractures in a patient on long-term alendronate. Hong Kong Med J. 2007; 13(6):485-489.
Goh SK, Yang KY, Koh JSB, et al. Subtrochanteric insufficiency fractures in patients on alendronate therapy. A caution. J Bone Joint Surg Br. 2007; 89(3):349-353.
Kwek EBK, Goh SK, Koh JSB, Png MA, Howe TS. An emerging pattern of subtrochanteric stress fractures: a long-term complication of alendronate therapy? Injury. 2008; 39(2):224-231.
Lenart BA, Lorich DG, Lane JM. Atypical fractures of the femoral diaphysis in postmenopausal women taking alendronate. N Engl J Med. 2008; 358(12):1304-1306.
Neviaser AS, Lane JM, Lenart BA, Edobor-Osula F, Lorich DG. Low-energy femoral shaft fractures associated with alendronate use. J Orthop Trauma. 2008; 22(5):346-350.
Sayed-Noor AS, Sjoden GO. Subtrochanteric displaced insufficiency fracture after long-term alendronate therapy—a case report. Acta Orthop. 2008; 79(4):565-567.
Schneider JP. Should bisphosphonates be continued indefinitely? An unusual fracture in a healthy woman on long-term alendronate. Geriatrics. 2006; 61(1):31-33.
Odvina CV, Zerwekh JE, Rao DS, Maalouf N, Gottschalk FA, Pak CYC. Severely suppressed bone turnover: a potential complication of alendronate therapy. J Clin Endocrinol Metab. 2005; 90(3):1294-1301.
Visekruna M, Wilson D, McKiernan FE. Severely suppressed bone turnover and atypical skeletal fragility. J Clin Endocrinol Metab. 2008; 93(8):2948-2952.
Black DM, Schwartz AV, Ensrud KE, et al. Effects of continuing or stopping alendronate after 5 years of treatment. The Fracture Intervention Trial Long-term Extension (FLEX): a randomized trial. JAMA. 2006; 296(24):2927-2938.
Khan SA, Kanis JA, Vasikaran S, et al. Elimination and biochemical responses to intravenous alendronate in postmenopausal osteoporosis. J Bone Miner Res. 1997; 12(10):1700-1707.
Ensrud KE, Barrett-Connor EL, Schwartz A, et al. Randomized trial of effect of alendronate continuation versus discontinuation in women with low BMD: results from the Fracture Intervention Trial long-term extension. J Bone Miner Res. 2004; 19(8):1259-1269.
Rodan G, Reszka A, Golub E, Rizzoli R. Bone safety of long-term bisphosphonate treatment. Curr Med Res Opin. 2004; 20(8):1291-1300.
Yang KH, Won JH, Yoon HK, Ryu JH, Choo KS, Kim JS. High concentrations of pamidronate in bone weaken the mechanical properties of intact femora in a rat model. Yonsei Med J. 2007; 48(4):653-658.
Ott SM. Editorial: long-term safety of bisphosphonates. J Clin Endocrinol Metab. 2005; 90(3):1897-1899.
Sebba A. Osteoporosis: how long should we treat? Curr Opin Endocrinol Diabetes Obes. 2008; 15(6):502-507.
Bone HG, Greenspan SL, McKeever C, et al. Alendronate and estrogen effects in postmenopausal women with low bone mineral density. Alendronate/Estrogen Study Group. J Clin Endocrinol Metab. 2000; 85(2):720-726.
Black DM, Cummings SR, Karpf DB, et al. Randomised trial of effect of alendronate on risk of fracture in women with existing vertebral fractures. Fracture Intervention Trial Research Group. Lancet. 1996; 348(9041):1535-1541.
Bone HG, Hosking D, Devogelaer JP, et al. Ten years’ experience with alendronate for osteoporosis in postmenopausal women. N Engl J Med. 2004; 350(12):1189-1199.

Authors

Drs Goddard, Reid, Johnston, and Khanuja are from the Department of Orthopedic Surgery, The Johns Hopkins University, Baltimore, Maryland.

Drs Goddard, Reid, Johnston, and Khanuja have no relevant financial relationships to disclose.

Correspondence should be addressed to: Harpal S. Khanuja, MD, c/o Elaine P. Henze, BJ, ELS, Medical Editor and Director, Editorial Services, Department of Orthopedic Surgery, Johns Hopkins Bayview Medical Center, 4940 Eastern Ave, #A6765, Baltimore, MD 21224-2780.

DOI: 10.3928/01477447-20090624-27

Cannulok Hip System

2009-08-25T05:08:00.000-07:00

Cannulok®Plus is the result of a continuing successful liaison between Orthodynamics, a UK based independent orthopaedic manufacturing company, and a group of dedicated surgeons. This relationship was first conceived in the early nineties, between Mr. Andrew Quaile FRCS, then practising at Southampton General Hospital, and Dr John Bradley, the then Managing Director of the company. The concept looked to utilise the technology associated with femoral nails and combine it with the potential to provide a revision hip solution in the treatment of periprosthetic fractures around either total hip or hemiarthroplasty implants. The implant design and product range have undergone significant enhancements since the Cannulok was first implanted as a straight stem with two distal locking holes. Perhaps the most notable development was the introduction of Left and Right anatomically sided stems in the late nineties. With the acquisition of the business, and subsequent integration into the Summit Medical group, considerable product development opportunities were identified for the Cannulok system. Following a Cannulok user group meeting, held in 2006 and chaired by Mr. David Ward FRCS Kingston Hospital, the outlines of the system we offer today took shape. This, combined with questionnaire feedback from a considerable number of users, confirmed the requirement for a more comprehensive product range to assist clinicians in the treatment of:

Grossly deficient proximal femurs as a result of osteolysis.
Femoral reinforcement where bone stock is depleted as a result of previous surgery.
Periprosthetic fracture around the trochanteric region of total and hemiarthroplasty implants.
Intraoperative fractures during hip arthroplasty.
Femoral fractures complicated by metastatic bone disease.
Paprosky IIIA & IIIB indications.

The Cannulok®Plus system, launched in January this year, is fully compliant with the Medical Device Directive’s Class III regulatory requirements due to come into force in September 2009; this makes it one of the first hip prostheses to meet the more stringent Class III criteria. A summary of the new features and benefits offered by the comprehensive Cannulok®Plus solution is detailed below: 45mm Offset:-
With the introduction of the 45mm offset, in every femoral stem size, clinicians can now be confident in more accurately replicating the patient’s anatomy and achieving improved stability. Whether the patient requires a large or small implant, there is a choice of ‘standard’ (nominal 40mm) or 45mm offset, ensuring that there is no compromise. The new 45mm offset stems also provide an increased proximal fill which increases the proximal stability of the stem, especially for Paprosky type III & IV (with impaction grafting), as well as providing a greater area for osseointegration. 360mm Length:-
The new 360mm stem, available in all stem diameters, allows secure fixation to be achieved well below the femoral isthmus, whether this is due to a distal fracture, or severe osteolysis precluding a diaphyseal fit. The 360mm stem fully complements the existing 240mm and 300mm stems, making it simple to select the correct implant, however distal the fracture may be. The Cannulok has always been available in lengths up to 400mm through a custom design service, though with increasing numbers of requests for longer stems to meet the increasing incidence of periprosthetic fractures around revision stems, there was a clear need to introduce a longer stem ‘off the shelf’. This allows this increasingly common problem to be dealt with as and when it is presented. 17mm Diameter:-
The expansion in stem diameters to 17mm completes the product range, allowing the clinical team to confidently treat an increasing number of patients whom require a large implant. This gives peace of mind that when treating any size femur, Cannulok®Plus will be the right system for a wide range of indications and patients anatomies, with distal stem diameters ranging from 11mm -17mm. Fully Coated:-
The Cannulok®Plus is now fully coated, with the full 90µm HA layer allowing better distal osseointegration, as well as increasing the rate at which progressive offloading of the distal fixation occurs. Instrumentation:-
Clearly a significant factor in the successful conclusion of every procedure, the instrumentation has been reviewed and upgraded to complement the enhanced product offering. Custom Implant Service
For extreme revision cases and unusual anatomy, the Cannulok®Plus can be especially tailored for individual patients. Common customisations include additional and intermediate lengths (up to 400mm), different diameters and variations to the anatomic bow. The company’s experienced design and manufacturing teams have a great track record of achieving the best possible result for every patient. Upon the provision of A-P and M-L X-rays, the custom Cannulok is quickly designed with the templated plans and implant drawings being sent to the surgeon for approval. The prosthesis can then typically be ready for surgery within two weeks of surgeon approval. This lead time can be further reduced if the implant is required without HA coating and in a non-sterile condition for critical procedures.

Overview of Platelet Rich Plasma Therapy

2009-08-22T09:58:00.000-07:00

About PRP Therapy

PRP therapy offers a promising solution to accelerate healing of tendon injuries and osteoarthritis naturally without subjecting the patient to significant risk. PRP is an emerging treatment in a new health sector known as "Orthobiologics." The philosophy is to merge cutting edge technology with the body's natural ability to heal itself.

Blood is made of RBC (Red Blood Cells), WBC (White Blood Cells), Plasma, and Platelets. When in their resting state, platelets look like sea sponges and when activated form branches. Platelets were initially known to be responsible for blood clotting. In the last 20 years we have learned that when activated in the body, platelets release healing proteins called growth factors. There are many growth factors with varying responsibilities, however cumulatively they accelerate tissue and wound healing. Therefore after increasing the baseline concentration of these platelets, we are able to deliver a powerful cocktail of growth factors that can dramatically enhance tissue recovery.
PRP History and Current Studies

PRP was initially used over 20 years ago in the Dental community to enhance wound healing in cancer patients with jaw reconstruction. Soon afterwards its applications extended across many fields of medicine from cardiovascular surgery to orthopaedics. Multiple studies are underway to help further refine the treatment and demonstrate its efficacy.

Clinical use of platelet-rich plasma in orthopaedics

2009-08-22T09:56:00.000-07:00

By Barbara D. Boyan, PhD; Zvi Schwartz, DMD, PhD; Thomas E. Patterson, PhD; and George Muschler, MD

The increasing use of platelet-rich plasma (PRP) in orthopaedics presents significant opportunities—as well as significant questions—about appropriate clinical applications for this developing therapy.

PRP was initially developed in the 1970s; recent technologic advances have enabled the administration of PRP to move from the hospital setting into outpatient and ambulatory surgical centers…even into physicians’ offices.

Although PRP therapy seems quite promising in several areas, it is not appropriate in all cases. A clear understanding of the repair response, the development of PRP therapy, and the variables that may affect the effectiveness of PRP therapy is necessary to make informed clinical judgments on its use.

A centrifuge is used to isolate the platelets, which are rich in growth factors.

The repair response
The repair response of musculoskeletal tissues generally starts with the formation of a blood clot and degranulation of platelets, which releases growth factors and cytokines at the site. This microenvironment results in chemotaxis of inflammatory cells as well as the activation and proliferation of local progenitor cells. In most cases, fibroblastic scar tissue is formed. In some settings, however, such as in a fracture callus, these conditions can also facilitate the formation of new bone tissue.

The following growth factors can be found in the environment of a blood clot:

* transforming growth factor beta (TGF-b)
* platelet-derived growth factor (PDGF)
* insulin-like growth factor (IGF)
* vascular endothelial growth factors (VEGF)
* epidermal growth factor (EGF)
* fibroblast growth factor-2 (FGF-2)

Many of these factors have been shown to enhance one or more phases of osteogenesis. PDGF, EGF, and FGF-2 have been shown to stimulate proliferation of osteoblastic progenitors. TGF-b increases matrix synthesis (eg, type I collagen) in vitro and in vivo. Angiogenic factors, including VEGF and FGF-2, can potentially enhance early angiogenesis and revascularization, as suggested by a recent study examining blood vessel formation in large segmental defects in the tibias of rats treated with platelet-rich plasma (PRP).1

Enriching a rich environment
The development of PRP focused on enhancing this rich environment. Could concentrated preparations of platelets or of platelet degranulation products increase the growth factors in the blood clot and be used to augment fracture repair or bone grafting sites? Existing technology enabled the isolation and concentration of the patient’s own platelets either before or during surgery. The result is an autologous PRP that contains a biologically active mixture of growth factors without the potential for an immune response.

Preclinical and clinical investigations have actively examined the possible usefulness of PRP preparations. Such studies recognize the possibility that the effect of the clot microenvironment or concentrates of PDFGs on fracture repair might be either positive or negative. The nature of this effect, like that of many graft materials, depends on the clinical setting, particularly the graft site’s local environment of cells in which PRP or associated factors are placed.

For example, clots also contain bone morphogenetic proteins (BMPs).2 Recent in vitro studies suggest that, although components of the platelet releasate stimulate migration and proliferation of osteogenic progenitor cells, they also inhibit the osteogenic action of BMPs.3,4

Because PRP preparations do not provide a source of autogenous osteogenic cells, their effects depend on the presence of a local osteogenic population. In addition to increasing the proliferation of osteoblastic cells and matrix synthesis, the growth factors associated with PRP also promote fibroblastic growth, differentiation, and scar formation. In many cases, they also inhibit later stages of osteoblastic differentiation.

Various methods are now commercially available for preparing PRP and a similar material called “autologous growth factor,” which is PRP plus the white blood cell buffy coat obtained during PRP preparation. As a result, assessment of these strategies in clinical orthopaedic practice has accelerated. Studies in the oral and maxillofacial surgery literature5 suggest that PRP can be an effective adjunct to some craniofacial bone graft procedures, but it appears to be most useful for soft-tissue applications.

Effectiveness “depends”
The literature on the clinical use of PRP suggests that considerable variability exists in its effectiveness, even in the same clinical setting. Several reasons may account for this variability.

PRP is donor dependent. A recent study examining the effect of PRP in combination with human demineralized bone matrix (DBM) highlighted multiple sources of variation.6 Researchers tested PRP from six young male donors with two different batches of human DBM using the nude mouse muscle implantation assay. The results showed that PRP reduced the effectiveness of the DBM in a donor-dependent manner. The effectiveness of the PRP also varied with the quality of the DBM, which is also donor dependent.7

The composition of PRP varies with the preparation technique used.8 Although all PRP preparations contain a basic set of growth factors, the relative concentration of each factor can differ among preparations. Moreover, the proteases present in the platelet releasate may degrade some of the growth factors,9 which reduces the availability of bioactive factors, and changes the composition of the PRP, altering its clinical effectiveness for specific applications.

These factors may help explain the different outcomes that result when PRP is used in orthopaedic applications. Recent studies using PRP to encourage healing after spinal fusion have been disappointing; the addition of PRP to bone graft seems to reduce the spinal fusion rate in animals as well as in humans.10,11 In contrast, a different study involving a canine spinal fusion model and the delivery of an enriched population of marrow-derived osteogenic connective tissue progenitors to the graft site found that the addition of a blood clot enhanced fusion and bone formation.12,13 Similarly, using the same types of grafts, the addition of PRP in a canine femoral defect model also enhanced bone formation.14

Use with care
In summary, available data suggest that PRP may be valuable in enhancing soft-tissue repair and in wound healing.15 However, the clinical role of PRP in bone repair remains controversial. PRP is not uniformly successful as an adjuvant to bone grafting procedures. PRP may promote or inhibit bone formation, depending on the setting in which it is used and the quality of the PRP.

Significant additional research is needed to define the role of PRP and to determine in which settings it might—or might not—be valuable. This may also involve defining a means of ensuring that a given PRP preparation is biologically active, by determining its critical component(s) and developing assays that can provide this information to the surgeon in a timely manner.

Barbara D. Boyan, PhD, and Zvi Schwartz, DMD, PhD, are members of the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, Atlanta; Dr. Boyan also holds an appointment in the Department of Orthopaedics at Emory University Medical School. Thomas E. Patterson, PhD, and George Muschler, MD, are from the Cleveland Clinic, in Cleveland, Ohio.

References

1. Rai B, Oest ME, Dupont KM, Ho KH, Teoh SH, Guldberg RE: Combination of platelet-rich plasma with polycaprolactone-tricalcium phosphate scaffolds for segmental bone defect repair. J Biomed Mater Res A 2007;81:888-899.
2. Sipe JB, Zhang J, Waits C, Skikne B, Garimella R, Anderson HC: Localization of bone morphogenetic proteins (BMPs)-2, -4, and -6 within megakaryocytes and platelets. Bone 2004;35:1316-1322.
3. Kark LR, Karp JM, Davies JE: Platelet releasate increases the proliferation and migration of bone marrow-derived cells cultured under osteogenic conditions. Clin Oral Implants Res 2006;17:321-327.
4. Gruber R, Kandler B, Fischer MB, Watzek G: Osteogenic differentiation induced by bone morphogenetic proteins can be suppressed by platelet-released supernatant in vitro. Clin Oral Implants Res 2006;17:188-193.
5. Ranly DM, McMillan J, Krause WF, Lohmann CH, Boyan BD, Schwartz Z: Platelet-rich plasma: A review of its components and use in bone repair, in Akay M (ed): Encyclopedia of Biomedical Engineering, vol 5. Hoboken, NJ: John Wiley & Sons, Inc., 2006, pp 2804-2815.
6. Ranly DM, Lohmann CH, Andreacchio D, Boyan BD, Schwartz Z. Platelet-rich plasma inhibits demineralized bone matrix-induced bone formation in nude mice. J Bone Joint Surg Am 2007;89:139-147.
7. Schwartz Z, Somers A, Mellonig JT, et al: Ability of commercial demineralized bone allograft to induce bone formation is donor age-dependent but not gender-dependent (abstract). Trans Orthopaed Res Soc 1997;22:230.
8. Weibrich G, Kleis WK, Hitzler WE, Hafner G. Comparison of the platelet concentrate collection system with the plasma-rich-in-growth-factors kit to produce platelet-rich plasma: A technical report. Int J Oral Maxillofac Implants 2005;20:118-123.
9. Thibault L, Beausejour A, de Grandmont MJ, Lemieux R, Leblanc JF: Characterization of blood components prepared from whole-blood donations after a 24-hour hold with the platelet-rich plasma method. Transfusion 2006;46:1292-1299.
10. Li H, Zou X, Xue Q, Egund N, Lind M, Bunger C: Anterior lumbar interbody fusion with carbon fiber cage loaded with bioceramics and platelet-rich plasma: An experimental study on pigs. Eur Spine J 2004;13:354-358.
11. Weiner BK, Walker M: Efficacy of autologous growth factors in lumbar intertransverse fusions. Spine 2003;28:1968-1970.
12. Muschler GF, Nitto H, Matsukura Y, et al: Spine fusion using cell matrix composites enriched in bone marrow-derived cells. Clin Orthop Relat Res 2003;(407):102-118.
13. Muschler GF, Matsukura Y, Nitto H, et al: Selective retention of bone marrow-derived cells to enhance spinal fusion. Clin Orthop Relat Res 2005;(432):242-251.
14. Brodke D, Pedrozo HA, Kapur TA, et al: Bone grafts prepared with selective cell retention technology heal canine segmental defects as effectively as autograft. J Orthop Res 2006;24:857-866.
15. Murray MM, Spindler KP, Ballard P, Welch TP, Zurakowski D, Nanney LB: Enhanced histologic repair in a central wound in the anterior cruciate ligament with a collagen-platelet-rich plasma scaffold. J Orthop Res 2007;25:1007-1017.

September 2007 AAOS Now
http://www.aaos.org/news/bulletin/sep07/research2.asp

Protein level may serve as predictor of severe osteoarthritis

2009-08-22T09:08:00.000-07:00

1st on the web (July 31, 2009)

A group of German, Austrian and Italian researchers reported this week that vascular cell adhesion molecule-1 (VCAM-1) is a strong predictor of hip and knee joint replacement due to severe osteoarthritis (OA).

The study appears in the August issue of Arthritis & Rheumatism.

Led by Georg Schett, MD, of the University of Erlangen-Nuremberg in Erlangen, Germany, the study involved 912 otherwise healthy individuals in Bruneck, Italy, 60 of whom underwent hip or knee replacement surgery due to severe OA in a 15-year follow-up period.
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MTJR

Subjects underwent a baseline exam in 1990, and investigators performed follow-up exams every 5 years until 2005, according to a press release. They also analyzed blood samples for VCAM-1, a sialoglycoprotein (a combination sugar and protein) expressed on cells in the cartilage and connective tissue.

The results showed that VCAM-1 levels were substantially elevated in the 60 individuals who underwent joint replacement, with the highest baseline levels seen in those who underwent bilateral joint replacement, according to the press release.

“The level of VCAM-1 emerged as a significant predictor of the risk of joint replacement due to severe OA, equaling or even surpassing the effects of age,” the authors said in the press release. They also noted that inclusion of VCAM-1 levels in risk prediction models resulted in a more accurate classification of individuals.

VCAM-1 promotes leukocyte adhesion and homing to sites of inflammation, according to the press release. In chondrocytes, VCAM-1 expression is induced by inflammatory cytokines (ie, proteins released by immune system cells).

The authors suggest that increased VCAM-1 levels may mirror active cartilage damage or an inflammatory component in OA. Since it mediates the interaction of chondrocytes with immune cells, VCAM-1 may also contribute to immune-mediated cartilage damage, according to the press release.

Establishing laboratory biomarkers of severe OA is important for a number of reasons. The standard risk factors of age and weight are not enough for accurate risk prediction, and since OA is a highly prevalent disease, it would be helpful to accurately identify those at greater risk of developing rapid progression or severe disease, the researchers reported.

Early diagnosis would also be beneficial because the disease is present before clinical symptoms are present. Finally, improved prediction of severe OA would help identify patients for treatment interventions such as aerobic exercise, strength training and weight loss and might also help tailor therapeutic measures, according to the release.

“Further clarification of the mechanism underlying the association between VCAM-1 level and OA may well contribute to a better understanding of disease etiology,” the authors said in the press release, adding that application of their findings in routine clinical practice would require further studies to duplicate the results.

Reference:

* Schett G, Kiechl S, Bonora E, et al. Vascular cell adhesion molecule 1 as a predictor of severe osteoarthritis of the hip and knee joints. Arthritis Rheum. 60;8:2381-2389.

Pharmacological Approaches for Pediatric Patients With Osteomyelitis: Current Issues and Answers

2009-08-22T09:04:00.001-07:00

By Amanda Geist, PharmD; Robert Kuhn, PharmD
ORTHOPEDICS 2009; 32:573

Recent studies suggest that the current dosing recommendations of 40 mg/kg to 60 mg/kg per day of vancomycin may not be adequate for the treatment of severe MRSA infections in children.

Previously, methicillin-resistant Staphylococcus aureus (MRSA) was a common pathogen in hospitals and rarely was a concern in the community. However, in recent years, community-acquired MRSA (CA-MRSA) has become increasingly prevalent in children.1,2 There are several therapeutic options for the treatment of CA-MRSA in the outpatient setting. Challenges that practitioners face when choosing an optimal regimen for pediatric patients are often related to patient age and preference. For children, in addition to matching “drugs to bug” combinations, the selection of the most optimal regimen requires consideration of several important factors, such as palatability, drug formulation, and cost.
Epidemiology

Osteomyelitis is an inflammatory process of the bone caused by bacterial or fungal infection. The overall incidence of osteomyelitis in children in the United States is unknown; however, the incidence has been reported as approximately 1 per 5000 children, accounting for approximately 1% of all pediatric hospitalizations.3,4 Half of all cases of osteomyelitis in children occur before 5 years of age.3 Boys are affected more commonly than girls, with a ratio of approximately 2:1.4
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Signs and symptoms of osteomyelitis vary depending on the child’s age and the affected area. For example, an older child may report pain and tenderness at the site of the infected area, but osteomyelitis in an infant who is unable to verbalize pain may manifest as guarding of the involved extremity or irritability.5 Other signs and symptoms include fever and swelling, warmth, and erythema of the infected area.5

The most common sites of involvement typically are long bones such as the tibia and femur, comprising approximately 20% to 30% of cases.6 Other less commonly infected sites include short bones, such as the ribs, clavicle, and scapula.6 The most common pathogens implicated in osteomyelitis are bacterial in nature, and the etiology of osteomyelitis in children is typically hematogenous spread, with infection caused by spread from trauma, surgery, or vascular insufficiency occurring much less frequently.5,6 Several pathogens may be involved in osteomyelitis, and in children it will vary depending on age and type of osteomyelitis involved. For example, the most common pathogens for children of any age are S aureus and Streptococcus pyogenes; while Kingella kingae and Streptococcus pneumoniae are more common in younger children.5,6
Prevalence

Recent studies have shown that osteomyelitis caused by CA-MRSA has increased complications compared with infection caused by methicillin-sensitive Staphylococcus aureus (MSSA) or other pathogens.7,8 These complications include increased need for surgical intervention, more febrile days, increased length of hospitalization, and increased duration of antibiotics.7,8 A rise in the number of cases of culture-proven CA-MRSA also has a direct impact on clinical case load and transition from the inpatient to outpatient setting.
Treatment Approaches

One of the most common empiric treatment options for MRSA in the inpatient setting is vancomycin. Vancomycin is a bacteriostatic glycopeptide that exerts its effects by binding to the precursors necessary in bacterial cell wall formation to inhibit cell wall synthesis. The spectrum of activity for vancomycin only includes Gram-positive organisms such as S aureus, Streptococci, and Enterococcus. Vancomycin is widely distributed; however, penetration into bone and cerebral spinal fluid is limited. Therefore, higher targeted serum concentrations, between 15 and 20 mcg/mL, are warranted in severe infections and those involving the central nervous system and bone.9,10 Due to its low oral bioavailability, only intravenous therapy can be used for the treatment of infections other than those involving Clostridium difficile.

Current empiric dosing guidelines for vancomycin in the treatment of osteomyelitis in children start at 40 mg/kg per day divided every 6 to 8 hours.10 However, a recent study conducted by Frymoyer et al11 proposed that 40 mg/kg per day may not be adequate for treatment of severe MRSA infections with minimum inhibitory concentrations of 1 mcg/mL. This study suggests initial empiric vancomycin doses of 60 mg/kg per day, depending on age, in children without underlying renal dysfunction.11 In addition, clinical experience at our institution has shown that the currently recommended dosing guidelines of 40 mg/kg to 60 mg/kg per day consistently produce trough concentrations below the goal range of 15 to 20 mcg/mL for treatment of serious infections, osteomyelitis, and abscess.

McCabe et al12 suggest that dosing ranging between 75 mg/kg and 95 mg/kg per day, depending on age (Tables 1, 2) and with close monitoring, is a more appropriate dosing schematic to reach goal serum concentrations in a timely manner.

Table 1: Initial Empiric Vancomycin Dosing Regimen Stratified by Age Proposed by McCabe et al

Table 2: Common Dosage Forms and Cost of Agents Used in the Treatment of MRSA Infections in Children

In an era of increased incidence of MRSA infections associated with increased complications, it is important to achieve rapid therapeutic serum concentrations. Prompt achievement of adequate serum concentrations will allow for more rapid stabilization of the treatment regimen and the potential for a faster transition to outpatient therapy, which can have a direct impact on patient case load.

Monitoring of vancomycin therapy should include reaching either serum trough concentrations alone or trough and peak concentrations 30 minutes prior to and 1 hour after the third or fourth dose of therapy, depending on local institutional practice.

Repeat trough concentrations should be conducted at least weekly for those who require therapy longer than 5 to 7 days. Other monitoring parameters should include daily assessment of blood urea nitrogen, serum creatinine, and urine output while on therapy, especially for patients taking other potentially nephrotoxic agents (eg, aminoglycosides).

The most common side effects seen with the use of intravenous vancomycin in the pediatric population involve infusion reactions. Patients can develop red man syndrome, a histamine-mediated infusion reaction characterized by flushing, rash, and hypotension.

Red man syndrome typically occurs with rapid infusions, those given faster than the conventional practice of over 1 hour. Red man syndrome can be minimized by premedicating with diphenhydramine and slowing the infusion rate to administer the dose over 90 to 120 minutes. It may be necessary to slow the infusion rate to administer higher doses proposed by McCabe et al12 over 1.5 to 2 hours to help prevent the development of red man syndrome.

Daptomycin is another potential treatment option for the inpatient management of CA-MRSA in pediatric patients. Daptomycin is a bactericidal lipopeptide antibiotic that acts by causing depolarization of the bacterial cell membrane to cause cellular death.13 It can be used in the treatment of complicated skin and soft tissue infections and bacteremia, and although it is not approved for use in osteomyelitis, case studies in adult populations have shown clinical cure rates of approximately 63% in the treatment of osteomyelitis.14 However because it is inactivated by lung surfactant, daptomycin should never be used in the treatment of pneumonia.13

Although relatively little information exists regarding the use of daptomycin in the pediatric population, case reports have demonstrated an 86% efficacy rate when used at doses ranging between 4 mg/kg to 6 mg/kg per dose given intravenously once daily for the treatment of bacteremia (Table 2).13 Advantages to its use include a once daily dosing regimen as well as a unique mechanism of action that provides coverage against resistant strains of Staphylococci such as MRSA and vancomycin-resistant Enterococci.

A potential side effect associated with daptomycin use is myopathy.13 Patients receiving daptomycin therapy should be monitored for signs and symptoms of muscle pain and weakness, and patients should have creatinine phosphokinase (CPK) levels drawn at least weekly during treatment.13

Several therapeutic options exist for the treatment of CA-MRSA in the outpatient setting. Challenges that practitioners face when choosing an optimal regimen for pediatric patients are often related to patient age and preference. For example, it is important to select an agent that is palatable, easily and accurately measured, and is available in various pharmaceutical dosage forms or able to be extemporaneously compounded into a liquid preparation for those unable to swallow capsules or tablets.

One therapeutic option is that children could receive intravenous antimicrobials in the outpatient setting. However, numerous constraints are associated with home intravenous therapy such as interference with the patient’s ability to perform activities of daily living. A recent study by Zaoutis et al15 that compared the use of prolonged intravenous therapy to early transition to oral therapy for the treatment of osteomyelitis in children showed that those patients who received prolonged intravenous therapy were more likely to experience treatment-related complications. In addition, this study also showed that those patients who received early transition to oral therapy were no more likely to experience treatment failure than those who received prolonged intravenous therapy.15

One of the most common treatment options for MRSA infections in children is sulfamethoxazole and trimethoprim. Each agent in sulfamethoxazole and trimethoprim (SMX-TMP) inhibits bacterial folic acid synthesis at different steps in the enzymatic process to allow for synergy. Its spectrum of activity includes Staphylococci, Streptococci, Escherichia coli, and Proteus, among others. Pathogens such as S aureus that may be resistant to sulfamethoxazole or trimethoprim alone are usually sensitive when used in combination. The traditional dosing recommendation for SMX-TMP in the treatment of pediatric infections is 6 mg/kg to 12 mg/kg per day in 2 divided doses based on the trimethoprim component.10 However, to achieve increased bone penetration; our institution uses doses ranging between 15 mg/kg to 20 mg/kg per day in divided doses up to a maximum of 960 mg per day of the trimethoprim component (Table 2).10

An advantage of SMX-TMP use in the pediatric population is that it is available in various dosage forms, including a commercially available grape flavored suspension containing 200 mg SMX and 40 mg TMP/5 mL.10 Another advantage to its use is that it is relatively inexpensive and available as a generic product. Although SMX-TMP is also available in an intravenous formulation, several problems are associated with its administration. Adequate reconstitution requires the product be diluted in a large volume of hypotonic fluid (D5W or D10W), which may be too large of a fluid volume for younger infants and children.10

The most common side effects associated with the use of SMX-TMP are gastrointestinal upset such as nausea and vomiting.10 Although potential exists for allergic reaction and skin rash that could progress to Stevens-Johnson syndrome, these reactions are rare.9,10

Clindamycin is another commonly used agent in the management of MRSA infections in children. Clindamycin is a derivative of lincomycin that exerts its action by suppressing bacterial protein synthesis. It is either bacteriostatic or bactericidal, depending on the concentration at the site of action. It has a wide spectrum of activity that is active against most Gram-positive aerobic organisms such as Streptococci and Staphylococci including most methicillin-resistant species. Its spectrum of activity also includes anerobic Gram-negative organisms such as Bacteroides fragilis and Fusobacterium; however, it does not possess any activity against aerobic Gram-negative organisms.

Clindamycin distributes extensively into different tissues, including bone, and will accumulate in abcesses.9 It is rapidly absorbed and has high bioavailability (approximately 90%) when administered orally, making the transition from intravenous to oral therapy easy.9,10 For the treatment of pediatric patients unable to swallow capsules, there is a commercially available oral solution of 75 mg/5 mL in addition to other intravenous and oral formulations available.10 The oral solution has the advantage of not requiring refrigeration and is stable at room temperature for 2 weeks after reconstitution.10 However, the oral solution has poor palatability and parents are often faced with the difficult task of administering a medication several times per day that tastes bad and is difficult to mask.

One mechanism of MRSA resistance to clindamycin is mediated via ribosomal methylase and can have clinically significant treatment implications. Resistance can be constitutive in which there is resistance to macrolides, lincosamides, and streptogramin (MLS), or it may be inducible in which lincosamides and streptogramin appear active. If the isolate is resistant to both erythromycin and clindamycin, then the resistance is constitutive. If the isolate is resistant to erythromycin and sensitive to clindamycin, it may carry inducible to MLS resistance and a disk dilution test (D-test) should be conducted. If the isolate is D-test positive, this indicates inducible MLS resistance, therefore, treatment should not include clindamycin.

The typical dose of clindamycin in the treatment of complicated skin and soft tissue infections and osteomyelitis in children is 10 mg/kg to 30 mg/kg per day in divided doses every 6 to 8 hours with a maximum dose of 1800 mg per day orally or 25 mg/kg to 40 mg/kg per day intravenously divided every 6 to 8 hours (Table 2).10 Intravenous doses as high as 4500 mg per day have been given in life-threatening situations.10

The difference between maximum doses of intravenous and oral therapy is due to the most common side effect of clindamycin, gastrointestinal upset and risk for pseudomembranous colitis. The most frequent manifestation of gastrointestinal upset is diarrhea, with incidence reported as being between 2% to 20%, and is more often associated with increasing doses.10 Other manifestations include abdominal pain and cramping, nausea, and vomiting.10 A mechanism by which parents can help to minimize the incidence of adverse gastrointestinal effects caused by clindamycin is to administer with food. Families can also encourage their children to eat yogurt during therapy to help maintain normal intestinal flora.

A third treatment option for the management of osteomyelitis in children is linezolid, which exerts its action early in the process of bacterial protein synthesis to prevent the formation of the ribosomal complex required for bacterial protein synthesis. Its unique mechanism of action also allows it to possess activity against many organisms that have developed other mechanisms of resistance such as methicillin-resistant Staphylococci, penicillin-resistant Streptococci and vancomycin-resistant Enterococci.

Linezolid distributes easily into tissues and has good penetration into bone, joint, fat, and muscle.16,17 It has excellent oral bioavailability that is close to 100%; allowing for easy intravenous to oral conversion in a 1:1 manner.10 Dosing for complicated skin and soft tissue infections and osteomyelitis in infants and children depending on age is 10 mg/kg per dose every 8 to 12 hours intravenous and orally up to a maximum of 600 to 1200 mg per day (Table 2).10 It also has the added advantage of not requiring dosage adjustment for renal impairment.10

Linezolid is available in various dosage forms including a powder for oral suspension that is stable at room temperature for a prolonged period, up to 21 days.10 This makes it an ideal agent to be used for those children whom may require a longer duration of therapy. One of the more rare side effects associated with linezolid use is peripheral and optic neuropathies. There have been case reports of its occurrence in adolescents treated for longer periods, as most cases reported are in those who are treated for >3 months.18 Another important aspect to consider with the use of linezolid is its cost. Linezolid is expensive and many insurance companies require a prior authorization.19

Inpatient primary empiric therapy is usually initiated with vancomycin, and depending on culture and sensitivity data, it may be transitioned to other oral agents such as sulfamethoxazole-trimethoprim, clindamycin, and linezolid. For children, in addition to matching drugs to bug combinations, the selection of the most optimal regimen requires consideration of several important factors such as palatability, drug formulation, and cost.
The Bottom Line

* Community-acquired MRSA has become increasingly prevalent in children.
* Recent studies suggest that the current dosing recommendations of 40 mg/kg to 60 mg/kg per day of vancomycin may not be adequate for the treatment of severe MRSA infections in children.
* Practitioners are faced with multiple challenges when selecting the optimal treatment regimen for MRSA infections in children, including selection of not only the proper drug to bug combination, but also several important factors such as palatability, drug formulation, and cost.

References

1. Paintsil E. Pediatric community-acquired methicillin-resistant Staphylococcus aureus infection and colonization: trends and management. Curr Opin Ped. 2007; 19(1):75-82.
2. Chen AE, Goldstein M, Carroll K, et al. Evolving epidemiology of pediatric Staphylococcus aureus cutaneous infection in a Baltimore hospital. Ped Emer Care. 2006; 22(10):717-723.
3. Vazquez, M. Osteomyelitis in children. Curr Opin Pediatr. 2002; 14(1):112-115.
4. Sonnen GM, Henry NK. Pediatric bone and joint infections. Pediatr Clin N Amer. 1996; 43(4):933-947.
5. Gutierrez K. Bone and joint infections in children. Pediatr Clin N Amer. 2005; 95(2);779-794.
6. Gutierrez K. Bone and joint infections. In: Long SS, Pickering LK, Prober CG, eds. Principles and Practice of Pediatric Infectious Diseases. New York, NY: Churchill Livingstone; 2008:474-482.
7. Saavedra-Lozano J, Mejias A, Ahmad N, Peromingo E, Arudura MI, Guillen S, et. al. Changing trends in acute osteomyelitis in children: impact of methicillin-resistant Staphylococcus aureus infections. J Pediatr Orthop. 2008; 28(5):569-575.
8. Hawkshead JJ, Patel NB, Steele RW, Heinrich SD. Comparative severity of pediatric osteomyelitis attributable to methicillin-resistant versus methicillin sensitive Staphylococcus aureus. J Pediatr Orthop. 2009; 29(1):85-90.
9. Hardman JG, Limbird LE. Goodman and Gillman’s The Pharmacological Basis of Therapeutics. New York, NY: McGraw Hill; 2001.
10. Taketomo CK, Hodding JH, Kraus DM. Pediatric Dosage Handbook. Hudson, OH: Lexi-Comp Inc; 2008.
11. Frymoyer A, Hersh AL, Benet LZ, Guglielmo JB. Current recommended dosing of vancomycin for children With invasive methicillin-resistant Staphylococcus aureus infections is inadequate. Pediatr Infect Dis J. 2009; 28(5):398-402.
12. McCabe T, Iocono J, Davis GA, Nelson C, Kuhn R. Evaluating the empiric dose of vancoycin in pediatric patients. Paper presented at: International PPAG/ACCP Meeting; April 24-28, 2009; Orlando, Florida.
13. Ardura M, Mejias A, Katz K, et al. Daptomycin therapy for invasive gram-positive bacterial infections in children. Pediatr Infect Dis J. 2007; 26(12):1129-1132.
14. Lamp KC, Friedrich LV, Mendez-Vigo L, Russo R. Clinical experience with daptomycin for the treatment of patients with osteomyelitis. Amer J Med. 2007; 120(10A):S13-S20.
15. Zaoutis T, Localio AR, Leckerman K, et al. Prolonged intravenous therapy versus early transition to oral antimicrobial therapy for acute osteomyelitis in children. Pediatrics. 2009; 123:636-642.
16. Lovering AM, Zhang J, Bannister GC, et al. Penetration of linezolid into bone, fat, muscle and haematoma of patients undergoing routine hip replacement. Antimicrob Agents Chemother. 2002; 50(1):73-77.
17. Rana B, Butcher I, Grigoris P, Murnaghan C, Seaton RA, Tobin CM. Linezolid penetration into osteo-articular tissues. Antimicrob Agents Chemother. 2002; 50(5):747-750.
18. Linam WM, Wesselkamper K, Gerber MA. Peripheral neuropathy in an adolescent treated with linezolid. Pediatr Infect Dis J. 2009; 28(2):149-151.
19. Cardinal Health. Pharmaceutical distribution. Available at: www.cardinal.com. Accessed May 12, 2009.

Authors

Drs Geist and Kuhn are from the University of Kentucky HealthCare, Lexington, Kentucky.

Drs Geist and Kuhn have no relevant financial relationships to disclose.

Correspondence should be addressed to: Amanda D. Geist, PharmD, 800 Rose St, H110, Department of Pharmacy, Lexington, KY 40536.

DOI: 10.3928/01477447-20090624-16

Hyaline-like tissue seen in defects treated with stem cells and platelet rich plasma

2009-08-22T09:02:00.001-07:00

Analysis showed a higher relation between Collagen I and II after stem cell treatments.
By Gina Brockenbrough
ORTHOPEDICS TODAY 2009; 29:28

MIAMI — Treating chondral defects with mesenchymal stem cells delivered in a scaffold with platelet-rich plasma may result in repair tissue with properties more similar to normal hyaline cartilage than the repair tissue seen in controls, the use of scaffolds alone or loading scaffolds with stem cells alone.

“The treatment of full-thickness chondral defects with a collagen scaffold, mesenchymal stem cells compromised to the chondrocyte lineage and platelet rich plasma shows promising results,” Alex Vaisman, MD, said during his presentation at the 8th World Congress of the International Cartilage Repair Society. “Nevertheless, none of the treatment groups healed with normal hyaline cartilage.”
ICRS

To evaluate the properties of repair tissue created after treating full-thickness chondral defects of the knee with a bi-layer collagen scaffold embedded with autologous mesenchymal stem cells (MSCs) induced to chondrocyte differentiation and platelet-rich plasma (PRP), Vaisman and his colleagues created 20 mm2 acute full-thickness chondral defects in 36 femoral condyles of adult male New Zealand White rabbits.

They randomly assigned the rabbits to the following four groups:

* Group 1 in which the lesion was left untreated;
* Group 2 in which surgeons implanted a scaffold without MSCs or PRP;
* Group 3 in which a scaffold containing MSCs was implanted; and
* Group 4 in which a scaffold contained MSCs and PRP.

The investigators sacrificed the rabbits after 6 months. They evaluated the femoral condyles macroscopically, histologically using hematoxylin-eosin and Toluidine Blue staining, and molecularly using quantitative real-time polymerase chain reaction of Collagen II/I and aggrecan/versican.
Evaluation

Rabbit knee with a scaffold
A rabbit knee with a scaffold containing mesenchymal stem cells and platelet-rich plasma.

Image: Vaisman A

Using macroscopy, the investigators discovered fibrous tissue without bony exposure in the control group.

“Groups 2 and 3 showed a hypertrophic, soft, irregular tissue covering the whole lesion,” Vaisman said. “Group 4 has similar- to normal-hyaline cartilage.”

Histology revealed that all of the groups had some fibrocartilage, but the investigators found no significant difference among the groups.

“However, groups 3 and 4 had a slightly more similar appearance to hyaline cartilage than the other groups,” Vaisman said.

Upon molecular analysis, the investigators discovered that groups 3 and 4 had a significantly higher relation between Collagen II and I compared to the other groups.

Alan J. Nixon, MD, a co-moderator of the session, noted that PRP can contain a variety of growth factors. “Do you know what you used for PRP?” Nixon asked. “Did you assay what factors were in that?”

Vaisman said that the investigators did not assess which growth factors were in the PRP or determine the concentrations of these growth factors.

For more information:

* Alan J. Nixon, MD, can be reached at Cornell University, College of Veterinary Medicine, C3-187 VMC, Ithaca, NY 14853; 607-253-3224; e-mail: ajn1@cornell.edu.
* Alex Vaisman, MD, can be reached at Orthopaedic Surgery Unit, Clínica Alemana de Santiago, and Faculty of Medicine, Universidad del Desarrollo, P.O. Box 3737, Santiago, Chile; (56-2) 210-11 11, 212-97 00; e-mail: avaisman@alemana.cl. They have no direct financial interest in any companies or products mentioned in this article.

Reference:

* Vaisman A, Figueroa D, Calvo R, et al. Treatment of full-thickness chondral defects with a collagen scaffold, mesenchymal stem cells compromised to the chondrocyte lineage and platelet rich plasma. Paper #9.2.7. Presented at the 8th World Congress of the International Cartilage Repair Society. May 23-26, 2009. Miami.

High-flexion Knee Designs: Is it all About the Implant?

2009-08-22T09:01:00.000-07:00

Author: Issaq Ahmed, SpR, Department of Orthopaedic and Trauma Surgery, Queen Margaret Hospital, Dunfermline

There is an ever increasing drive to increase the range of movement after total knee arthroplasty (TKA). Some cultures all but demand it, some surgeons feel their technique enhances it, and many companies state that their design promotes it. The major goal of a primary TKA is to relieve pain whilst providing an adequate range of movement for activities of daily living. Range of movement following TKA, however, determines whether patients can manage high flexion activities such as crouching, kneeling or rising from the floor.

There are many factors other than prosthetic design, which influence flexion after TKA 1. Female gender, higher body mass index, previous surgery and other co-morbidities are associated with reduced flexion 2 while intra-operative factors such as component malposition, ‘overstuffing’ the patellofemoral joint by inserting oversized components, inadequate flexion gap balancing, failure to remove posterior osteophytes and inattention to patellofemoral tracking and thickness have been reported to have a negative effect 1. Most consistently however, the literature reports pre-operative range of movement as the best predictor of post operative range of movement 3. It has been suggested that those patients whose preoperative range of flexion was less than the mean tend to gain flexion postoperatively, whereas those with preoperative flexion greater than the mean tended to lose flexion 4. Thus there is a migration towards a mean post operatively from a broad spectrum of flexion before surgery.

The debate between whether to preserve or substitute the posterior cruciate ligament in total knee arthroplasty in order to gain flexion continues with several reviews of the literature finding insufficient evidence to recommend either 5. An implant which can achieve a deep flexion angle whilst maintaining stability has been the focus of research lately. These high-flexion prostheses include features such as reduced posterior femoral condylar radii, modifications in tibial and femoral components to accommodate extensor mechanisms with deep flexion and facilitation of physiological posterior femoral rollback. This article aims to summarise the current published studies comparing high flexion designed TKAs versus standard TKAs in order to determine whether we should be using these implants for high flexion demanding patients.

What is a high-flex knee?
Figure 1: Design features of the NexGen LPS-Flex knee. Detailing the extra 2mm bone resection of the posterior condyles. Taken from Huang et al. The early results of high flex TKA. J Arthroplasty 2005.
The initial concept came from Walker and Sathasivam 7 who reported that by increasing the thickness of the posterior condyle of the femoral component may overcome the edge loading and resultant increased posterior polyethylene wear and damage. The high flex design has a smaller femoral radius of curvature and thicker posterior condyle. In theory the smaller femoral radii of curvature increases the contact area between the posterior femoral condyle and the tibial insert. In addition to the thicker posterior condyle the NexGen LPS Flex (Zimmer, Warsaw, IN, USA) has a modified cam/post mechanism and an anterior cut out slope in the polyethylene insert to allow increased jump distance whilst avoiding dislocation at deep flexion angles.

Meta analysis
A recent review of the literature revealed several studies (Table 1) evaluating the effectiveness of high flexion implants in TKA 7-14. However of these nine studies only three 12, 14, 15 were prospective randomised controlled trials whilst the others were observational studies 7-11, 13. Five studies 7, 9, 10-12 reported greater flexion or range of motion with the High Flexion implant; however, the methodological rigour was questionable with inadequate blinding, flawed participant selection, short follow-up periods and functional outcomes which lacked sensitivity.

Figure 2. Lateral views of the NexGen CR-Flex (left) and NexGen LPS-Flex (right) prostheses. Extension of the radius and thickness (2 mm) of the posterior condyle in both systems increases the articular contact area at high flexion angles and thereby increases posterior femoral translation and the range of flexion. [Pictured adapted from Functional Outcome and Range of Motion of High-Flexion Posterior Cruciate-Retaining and High-Flexion Posterior Cruciate-Substituting Total Knee Prostheses A Prospective, Randomized Study. Kim et al. JBJS Am 2009]
The results were presented as either range of flexion or range of motion measured pre operatively and at the latest follow up. Only 2 studies 14-15 measured intraoperative flexion using the drop test. Three of the seven studies which investigated the LPS-Flex (Zimmer, Warsaw, IN, USA), the single studies involving the PFC Sigma RP-F (DePuy Orthopaedics, Inc., Warsaw, IN, USA) and the Genesis II High-flex PS (Smith & Nephew, Memphis, TN, USA) showed significant gains in their respective trials.

Functional outcome measures were reported in eight studies, the most common being the Knee Society Score (KSS) in five studies 7, 9, 10, 12, 14 and the Hospital for Special Surgery (HSS) Knee Score in two studies 8,11 while one study used both 15. Nutton et al. 14 also evaluated maximal functional knee flexion measured by electrogoniometry during various tasks. None of these studies showed any significant differences between the groups with these scores (p>0.05).

Table 1 – Summary of the current published literature.
Implant
used Study
design n
(patients) Follow up (years)
Huang (2005) 7 LPS Case controlled
LPS-F (retrospective) 28(28) 2
Seon (2005) 8 LPS Case Controlled 50(50) 2
LPS-F
Gupta (2006) 9 PFC Sigma Case controlled 50(45) 1
PFC Sigma RP-F 50(45)
Laskin (2007) 10 Genesis II PS Case controlled 40(40) 2
Genesis II High flex 40(40)
Bin (2007) 11 LPS Case Controlled 97(69) 1
LPS-F 96(72)
Weeden (2007) 12 LPS RCT 25(25) 1
LPS-F 25(25)
Ng (2008) 13 LPS Case Controlled 35(35) 2
LPS-F bilateral 35(35)
Nutton (2008) 14 LPS RCT 28(28) 1
LPS-F (Double blinded) 28(28)
Kim (2009) 15 LPS RCT, bilateral 250(125) 2
LPS-F 250(125)

n - number of implants (number of patients).
RCT – randomised controlled trial.
By far the largest Level 1 prospective double blind randomised controlled study by Kim et al 15 investigated whether there was an advantage to using either a posterior cruciate-retaining or posterior cruciate-substituting design. Two hundred and fifty patients received a high-flexion posterior cruciate retaining prosthesis in one knee and high-flexion posterior stabilised total knee prosthesis in the contralateral knee. Patients were assessed clinically by determining range of motion, both radiographically and functionally, with use of the knee rating systems of the Knee Society and the Hospital for Special Surgery. In addition, each patient completed the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) questionnaire. The authors found no difference in the ROM or in the clinical and radiographic results between knees that received a high-flexion cruciate-retaining or stabilized prosthesis.

The major strength of this study was that the patients acted as their own controls. Furthermore, patients were assessed clinically, radiographically, and by functional outcome by an independent observer. In addition all of the operations were carried out by one surgeon. Weaknesses of the study were that this was an Asian population of predominantly female patients and that the findings may not necessarily be transferable to other populations. In addition, when bilateral procedures are performed, it may be difficult to separate the functional outcome for one of the individual knees.

There are concerns that efforts to increase maximum flexion may negatively impact implant survival. Ranawat noted that shortening the posterior radius by removing more bone would result in instability and increased patellar and tibial stresses [16]. Other authors have shown increasing contact stresses with increasing flexion and translation of the femoro-tibial contact point, leading to potentially greater wear and earlier failure of polyethylene inserts [17, 18]. This is particularly concerning with the growing proportion of younger patients with higher functional demands receiving TKA.

Conclusion
This article set out to answer the question as to whether we should be using High flexion implants in patients who already have good ROM prior to their knee replacement or in the ‘High flexion user’. However, the current evidence for the improved clinical benefit of using these implants in TKA over traditional implants is conflicting. More importantly none of the studies reviewed investigated the effect of these implants in patients who have good ROM (>120 degrees) prior to their surgery. Further long term studies focusing particularly on these high flexion patients are required to determine whether these patients truly benefit from these implants. The hypothesis being that those patients with good flexion prior to surgery should go on to achieve the same flexion with or without a high flexion designed implant.

There may be no doubt that theoretically High Flex design total knee replacements should help gain or increase range of motion after TKA. Methodological limitations, inconsistencies in high flexion TKA published research along with uncertain long term survivorship lead me to conclude that there is currently no established benefit in post operative knee ROM or physical function when using a High flexion implant.

References

1. Dennis DA, Komistek RD, Scuderi GR, Zingde S (2007) Factors affecting flexion after total knee arthroplasty. Clin Orthop Relat Res 464:53–60
2. Fisher DA, Dierckman B, Watts MR, Davis K (2007) Looks good but feels bad: factors that contribute to poor results after total knee arthroplasty. J Arthroplasty 22(6 Suppl 2):39–42
3. Ritter MA, Harty LD, Davis KE et al (2003) Predicting range of motion after total knee arthroplasty. Clustering, log-linear regression, and regression tree analysis. J Bone Joint Surg Am 85:1278–1285
4. Scott RD, Volatile TB. Twelve years’ experience with posterior cruciate-retaining total knee arthroplasty. Clin Orthop Relat Res. 1986; 205:100-7.
5. Argenson JN, Scuderi GR, Komistek RD et al (2005) In vivo kinematic evaluation and design considerations related to high flexion in total knee arthroplasty. J Biomech 38:277–284
6. Walker PS. Sathasivam S. Design forms of total knee replacement. IMechE 2000 Vik 214(H): 101-119
7. Huang HT, Su JY, Wang GJ. The early results of high-flex total knee arthroplasty: a minimum of 2 years of follow-up. J Arthroplasty 2005. 20:674–679
8. Seon JK, Song EK, Lee JY (2005) Comparison of range of motion of high-flexion prosthesis and mobile-bearing prosthesis in total knee arthroplasty. Orthopedics 28(10 Suppl):s1247–s1250
9. Gupta SK, Ranawat AS, Shah Vet al (2006) The P.F.C. sigma RPF TKA designed for improved performance: A matched-pair study. Orthopedics 29(9 Suppl):S49–S52
10. Laskin RS. The effect of a high-flex implant on postoperative flexion after primary total knee arthroplasty. Orthopedics 2007: 30(8 Suppl): 86–88
11. Bin SI, Nam TS. Early results of high-flex total knee arthroplasty: comparison study at 1 year after surgery. Knee Surg Sports Traumatol Arthrosc 2007: 15:350–355
12. Weeden SH, Schmidt R. A randomized, prospective study of primary total knee components designed for increased flexion. J Arthroplasty 2007: 22:349–352
13. Ng FY, Wong HL, Yau WP et al Comparison of range of motion after standard and high-flexion posterior stabilised total knee replacement. Int Orthop 2008: 32:795–798
14. Nutton RW, van der Linden ML, Rowe PJ et al (2008) A prospective randomised double-blind study of functional outcome and range of flexion following total knee replacement with the NexGen standard and high flexion components. J Bone Joint Surg Br 90:37–42
15. Kim YH, Choi Y, Kwon O-R and Kim JS. High-Flexion Posterior Cruciate-Substituting Total Knee Prostheses. A Prospective, Randomized Study. J Bone Joint Surg Am. 2009; 91:753-60
16. Ranawat CS (2003) Design may be counterproductive for optimizing flexion after TKR. Clin Orthop Relat Res 416:174–176
17. Han HS, Kang SB, Yoon KS (2007) High incidence of loosening of the femoral component in legacy posterior stabilised-flex total knee replacement. J Bone Joint Surg Br 89:1457–1461
18. Akagi M, Nakamura T, Matsusue Y et al (2000) The Bisurface total knee replacement: a unique design for flexion. Four-to-nine year follow-up study. J Bone Joint Surg Am 82:1626–1633

The Biomechanical Evidence for Valgus Knee Bracing in Medial Compartment Osteoarthritis

2009-08-22T09:00:00.002-07:00

Author: Jim Richards, Professor of Biomechanics, School of Public Health & Clinical Sciences, University of Central Lancashire

Introduction
The use of knee orthoses to correct and to support moments about joints is one of the most common uses of direct orthotic management. In the case of knee valgus braces the aims are to unload the painful compartment through bending moments applied proximally and distally to the knee joint and to reduce the varus deformity (Pollo, 1998). Several studies have been conducted into the use of valgus knee braces for medial compartment osteoarthritis and have reported that patients experience significant pain relief and an improvement in physical function (Hewett et al, 1998; Kirkley et al, 1999; Lindenfeld et al, 1997; Matsumo et al, 1997; Richards et al 2005) and also a reduction in medial compartment load (Pollo et al, 2002; Jones et al, 2006).

But how can a valgus brace reduce the load on the medial compartment of the knee? The answer is that this is a very hard thing to measure directly; however, measures that give an indirect indication of the loading on the medial compartment are a reduction in the knee adduction moments and the varus angle of the knee.

It is widely known that knee osteoarthritis is more prevalent in the medial compartment of the knee joint than the lateral compartment and it has been estimated that during normal gait approximately 60–80% of the load across the knee joint is transmitted to the medial compartment (Prodromos et al, 1985).

During walking, individuals have an almost continuous large, external varus moment about their knees throughout stance phase, with the exception of a small valgus moment at initial contact (Johnson et al, 1980, Matsumo et al, 1997). It has been suggested that this varus or adduction moment and the increased loads are a causation factor for the incidence of medial compartment osteoarthritis (Goh et al, 1993). These increasing loads have a degenerative effect on the cartilage in the medial compartment with a narrowing in the joint space between the medial femur and medial tibial plateau. This causes a moment arm increased over that of the unaffected side in a control population (Wang et al, 1990). Increasing disability will therefore arise from the increased moment arm with pain and functional impairment being the principal complaints of knee osteoarthritis sufferers (Kim et al, 2004), ultimately leading to a reduced quality of life.

Treatment options available to the sufferer are aimed at minimizing these forces at the medial compartment of the knee (Pollo, 1998). Surgical options such as high tibial osteotomy (HTO) and unicompartmental arthroplasty attempt to unload the medial compartment by realigning the tibia, and decrease the loading at the medial compartment by transferring the load to the less affected lateral compartment (Maly et al, 2002; Noyes et al, 1992).

However, these types of surgery may not be appropriate for many individuals, therefore conservative treatment modalities have been introduced in an attempt to reduce this excessive compartmental loading without the need for surgical intervention. One form of conservative treatment for medial compartment osteoarthritis of the knee is valgus bracing. Valgus braces often claim more than just the ability to support and often claim to offload the painful compartment, correct the varus alignment of the knee and improve quality of life. Various studies have investigated the biomechanical effects and the pain reduction using such devices.

Biomechanical Changes seen with Valgus Bracing
Varus knee angle
The effect of valgus bracing on knee varus has been a point of debate for some time; however, recent research (Pollo et al, 2002; Jones et al, 2006) has shown that bracing can have a direct effect on the knee angulation in the coronal plane. The data below show the immediate effect of an individual with medial compartment knee OA walking with and without a valgus brace. The brace fitted in this instance was an OA Adjuster (DJO), which allows the clinician to dial in a ‘correction’. In this case the brace was adjusted until contact was made with the lateral aspect of the knee joint, and then a further 5° was dialed in.

This was to first take up the slack in the brace, and then to try to correct by a further 5°. The greatest effect in the varus angle is during loading response from 0 to 20% of the gait cycle (Figure 1). At approximately 10% of the gait cycle, the point of greatest loading, the difference between the braced and unbraced conditions was 4°, indicating that actual correction is in a similar order to the dial in correction, which in turn will reduce the moment arm of the ground reaction force in the coronal plane.

Figure 1: Varus angle from 0 to 50% of the gait cycle

Knee adduction moments
Kim et al (2004) looked at the adduction moment in individuals with and without medial compartment knee osteoarthritis. They found a significant difference in the adduction moment between the osteoarthritis group and an age and gender matched normal group; the osteoarthritis group having on average a 50% increase in their adduction moments. Kim also found a correlation between knee adduction moments with the WOMAC Score. This supports the comments by Goh et al (1993), who suggested that the adduction moment and the increased loads are a causation factor for the incidence of medial compartment osteoarthritis. The reduction in the varus deformity during loading, should in turn lead to a reduction in the adduction moment about the knee joint. Figure 2 shows that this is indeed the case, with the braced condition reducing the adduction moment by 13%.

Figure 2: Adduction moments normalized to body mass

Ground reaction forces
Ground reaction forces give useful information about the loading and propulsion during walking. For both the vertical and anterior posterior forces, increases in the loading and propulsive forces are seen (Figure 3) when wearing the valgus brace. But isn’t an increase in force bad? The ground reaction forces do not tell us much about the loading patterns within the knee; however, they are useful in determining how well an individual can load and push off during walking, the larger vertical loading and propulsive forces indicating an improved weight acceptance and propulsion.

Figure 3: Vertical and anterior posterior forces with and without bracing normalized to body weight

Summary and Conclusion
Overall, these findings show that valgus bracing can give a degree of correction to the varus deformity of the medial compartment osteoarthritic knee and a reduced adduction moment, which gives the subject substantial functional improvements during gait. Although this appears to be very clear evidence for the mechanical effect of valgus bracing, further research is needed on the effect of different designs and different amounts of correction. Can we, for instance, get the same amount of correction using a smaller brace, and what is the limit of correction we can achieve either by building the correction into the brace or by dialing the correction into the brace?

References

* Goh JC, Bose K, Khoo BC. Gait analysis study on patients with varus osteoarthrosis of the knee. Clinical Orthopaedics and Related Research 1993;(294):223–231.
* Hewett TE, Noyes FR, Barber-Westin SD, Heckmann T. Decrease in knee joint pain and increase in function in patients with medial compartment arthrosis: a prospective analysis of valgus bracing. Orthopedics 1998;21:131–138.
* Johnson F, Leitl S, Waugh W. The distribution of load across the knee. A comparison of static and dynamic measurements. British Journal of Bone and Joint Surgery 1980;62(3):346–349.
* Jones RK, Nester CJ, Kim WY, Tyson S, Laxton P, Jari S, Johnson D, Richards JD. Direct and indirect orthotic management of medial compartment osteoarthritis of the knee, ESMAC & GCMAS meeting, Amsterdam, 25–30 September, 2006.
* Kim WY, Richards JD, Jones RK, Hegab A. Single limb stance adduction moment in medial compartment osteoarthritis of the knee. The Knee 2004;11:225–231.
* Kirkley A, Webster-Bogaert S, Litchfi eld R, Amendola A, MacDonald S, McCalden R, Fowler P. The effect of bracing on varus gonarthrosis. American Journal of Bone and Joint Surgery 1999;81–A:539–548.
* Lindenfeld TN, Hewett TE, Andriacchi TP. Joint loading with valgus bracing in patients with varus gonarthrosis. Clinical Orthopaedics 1997; 344:290–297.
* Maly MR, Culham EG, Costigan PA. Static and dynamic biomechanics of foot orthoses in people with medial compartment knee osteoarthritis. Clinical Biomechanics (Bristol, Avon) 2002;17(8):603–610.
* Matsumo H, Kadowaki K, Tsuji H. Generation II knee bracing for severe medial compartment osteoarthritis of the knee. Archives of Physical Medicine and Rehabilitation 1997;78:745–749.
* Noyes FR, Schipplein OD, Andriacchi TP, Saddemi SR, Weise M. The anterior cruciate ligament-deficient knee with varus alignment. An analysis of gait adaptations and dynamic joint loadings. American Journal of Sports Medicine 1992;20(6):707–716.
* Pollo FE, Otis JC, Backus SI, Warren RF, Wickiewicz TL. Reduction of medial compartment loads with valgus bracing of the osteoarthritis knee. American Journal of Sports Medicine 2002;30:414–421.
* Pollo FE. Bracing and heel wedging for unicompartmental osteoarthritis of the knee. American Journal of Knee Surgery 1998;11:47–50.
* Prodromos CC, Andriacchi TP, Galante JO. A relationship between gait and clinical changes following high tibial osteotomy. American Journal of Bone and Joint Surgery 1985;67(8):1188–1194.
* Richards J, Sanchez-Ballester J, Jones RK, Darke N. A comparison of the effectiveness of two knee braces in the treatment of subjects with medial compartment osteoarthritis of the knee during walking. Journal of Bone and Joint Surgery, 7: 937-939, 2005.
* Wang JW, Kuo KN, Andriacchi TP, Galante JO. The influence of walking mechanics and time on the results of proximal tibial osteotomy. American Journal of Bone and Joint Surgery 1990;72(6):905–909.

Computer Navigation in Total Knee Arthroplasty

2009-08-22T09:00:00.001-07:00

Authors: Ayaz Lakdawala MRCS, MBBS - SpR - Trauma & Orthopaedics, Royal Orthopaedic Hospital, Birmingham
Nick Rouholamin MRCS - SpR - Trauma & Orthopaedics, Russells Hall Hospital, Dudley
Nadim Aslam FRCS (Orth) - Consultant Orthopaedic Surgeon - Worcestershire Royal Hospital, Worcester

Introduction
Component alignment and ligament balancing are critical factors in achieving a successful functional outcome following TKA1. Malalignment is an important cause of early failure. This can cause pain, instability, reduced range of movement, excessive polyethylene wear, and subsequent implant loosening. Conventional instrumentation uses anatomical bony landmarks. Reference errors with these landmarks can occur because these are either invisible (e.g., femoral head), virtual (e.g., mechanical axis) and difficult in the presence of associated deformities. Computer-assisted surgery (CAS) technology allows intra-operative quantitative measurements of axes. This information assists the surgeon in achieving component alignment and improved balancing of the knee, thereby avoiding the “outliers” in the alignment of the mechanical axis.

CAS: The Technology
Overall there are two mainstream technologies in current use: image based and imageless CAS. The former usually uses fluoroscopic assistance and has the ability to create a spatial link between the image and anatomical landmarks, the defined virtual points, planes, and axes. This enables the surgeon to visualise the fluoroscopic image of the implants intra-operatively and has control of every step in the procedure. Thus, with an image-based system, the surgeon can define the landmarks kinematically as well as visually. However, this has certain drawbacks. The fluoroscope is bulky, needs larger operating field & there is a potential radiation hazard. The imageless CAS is cheaper, less bulky, and easier to use.

In CT-based systems, scans are obtained pre-op and, intra-operatively the surgical field is registered and defined using either a surface-based or point-based system. Surface-based registration can provide a virtual 3D image and also provides assessment of bone density. This technique uses more radiation and can be costly.

The alternative is an image-free navigation. In this technique, the key anatomical references points (centre of the hip and ankle) are digitised by the surgeon. Accuracy is user dependent & complete 3D images cannot be obtained.

‘Bone Morphing’ is a newer technique and it provides complete 3D images. The computer computes the points digitised on the articular surfaces of the tibia and/or femur. Here the registration is done intra-operatively between the anatomical data and the statistical model. It cannot provide information on bone-density.

Virtual fluoroscopy is a system which does not require a registration procedure. The principle is to navigate on calibrated fluoroscopy images. After two to three images are acquired, the C-arm is removed. The images are 2-dimensional and expose the staff to radiation.

For the femoral component, the CAS technology provides the surgeon with precise information on flexion/extension and varus/valgus. For the tibial component, it provides more precise information regarding the orientation of tibial slope and varus/valgus positioning. This can assist in achieving more precise alignment and flexion/extension balancing of the knee.

Computer Assisted TKR Vs Conventional TKR
Different authors have published their experiences with these systems. A recent meta-analysis has shown more accurate AP & lateral alignment of the tibial and femoral components with fewer outliers outside the range of 3° varus or valgus 3. Some studies have shown no clinically significant difference between CAS & conventional TKR 4-6.

Sikorski 7 highlighted the limitations of the CAS to help identify rotational malalignment. Correct rotational alignment of a TKA is important to achieve optimal patellar tracking and implant longevity. In a randomised study, Lutzner et al 8; did not find any notable difference between CAS and conventional TKR techniques with regards to rotational alignment of the femoral or tibial components.

There is a steep learning curve, not only for the surgeon but also for the nursing staff. The operating time with CAS is longer than conventional technique because of the set-up and data acquisition 2. Most studies show not difference in blood-loss between the CAS and conventional technique. Functional results are also similar at 2 yrs 9. At present there is no long-term follow-up available on TKR using CAS technology.

BrainLAB’s knee essential software

CAS in Revision TKR
Common cause of revision TKR is aseptic loosening of the tibial components and instability due to inadequate balancing of the flexion/ extension gaps. In revision surgery the challenge is restoring the joint line and stability. This can be complicated by associated bone loss and difficulty in identifying relevant bony landmarks. CAS can help aid alignment and restore the joint line, however further information on CAS in revision TKR is required in the literature.

Future Challenges
Different CAS imaging modalities are emerging. Recently bone morphing has been introduced, allowing visualisation of a 3D surface of the bone intra-operatively. Accuracy of these new technologies needs to be clinically validated and devices need to be regulated. What is needed is a CAS system that does not require pre-operative imaging, allows 3D reconstruction, uses percutaneous techniques of registration and is easy to use. It would be desirable to have a system that also facilitates minimally invasive TKR.

Summary
CAS is still evolving and new technologies are emerging. It has a definite advantage in achieving precise component alignment but there is a learning curve. It can be particularly useful in planning TKR in presence of deformities around the knee.

It remains to be seen whether long-term results of TKR can be improved using CAS technology. It is possible that in the future, CAS will be more widely used especially as the new generation of trainees will most likely “grow up” with this concept and practice.

References

1. Insall JN. Surgery of the knee. 2nd Edition . New York: Churchill Livingstone, 1993.
2. Victor, J. Computer assisted surgery: Coronal and sagittal alignment. In Total Knee Arthroplasty: A Guide to Get Better Performance, edited by J. Bellemans, M. D.Ries, J.Victor, Springer, New York.
3. Bauwens K, Matthes G, Wich M, et al. Navigated total knee replacement: a meta-analysis. J Bone Joint Surg [Am] 2007; 89-A:261-9
4. Ensini A, Catani F, Leardini A, et al. Alignments and clinical results in conventional and navigated total knee arthroplasty. Clin Orthop 2007; 457:156-62.
5. Stulberg SD, Yaffe MA, Koo SS. Computer- assisted surgery versus manual total knee arthroplasty: a case controlled study. J Bone Joint Surg [Am] 2006; 88-A (Suppl 4): 47-54.
6. Kim YH, Kim JS, Yoon SH. Alignment and orientation of the components in total knee replacements with and without navigation support: a prospective, randomised study. J Bone Joint Surg [Br] 2007; 89-B:471-6.
7. Sikorski, J. M. Computer assisted surgery and rotational alignment of total knee arthroplasty. In Total Knee Arthroplasty: A Guide to Get Better Performance, chap. 40, edited by J. Bellemans, M. D. Ries, J. Victor, Springer, New York, 2005.
8. Lutzner J, Krummenauer F, Wolf C, Gunther K.P., Kirshner S. Computer-assisted and conventional total knee replacement. A comparative, prospective, randomised study with radiological and CT evaluation. J Bone Joint Surg [Br] 2008;90-B:1039-44.
9. Spencer JM, Chauhan SK, Sloan K, Taylor A, Beaver RJ. Computer- navigation versus conventional total knee replacement: no difference in the functional results at two years. J Bone Joint Surg [Br] 2007; 89-B: 477-80.

Locking Plate

2009-07-27T06:55:00.000-07:00

Locking plates are a popular method of internal fixation. Locking plates are most often used as a bridging plate in fractures with bone loss and short articular fragments.

The working length of a plate includes the portion of the plate that is unsupported by bone. The longer the segment of unsupported bone, the greater is the risk of failure.

Locking plates have become a popular, effective method of stabilizing metaphyseal/epiphyseal fractures with comminution and short articular fragments.

Important biomechanical features of locking plates include1:

* Locked screws can function as individual blade plates in the distal fragment.
* Locking plates can effectively serve as bridge plates, providing excellent fixation in short distal articular fragments.
* Compression of the plate against the bone is less than that of conventional plating, resulting in less devascularization of the underlying cortex.
* There is no toggling between the locked screws and the plate.
* The pullout strength of a locked unicortical screw is approximately 60% of a standard bicortical screw.
* Locking plates are similar biomechanically to an external fixator.
* Moment arms are less because the plate is closer to the bone's neutral axis than the connecting bar of the external fixator.

Intra-articular and Soft Tissue Steroid Injections

2009-07-27T06:52:00.000-07:00

Indications

1. Osteoarthritis and inflammatory arthritis
2. Meniscal tears
3. Tendinitis
4. Tenosynovitis

Contraindications

1. Infection
2. Allergy to steroids or lidocaine
3. Warfarin therapy
1. International normalized ratio (INR) > 4.5

Complications

1. Transient increase in pain (most common)
1. Occurs in approximately 5% of patients
2. Subsides within 24 hours
3. May be caused by the less soluble steroids
2. Skin and subcutaneous tissue atrophy
3. Depigmentation
4. Systemic effects (fairly common)
1. Usually mild and resolve quickly
2. Flushing, slight agitation
3. May worsen glucose control in patients with diabetes
5. Adrenal suppression (when given more than 1 to 2 times per month)
6. Infection occurs in 1 in 10,000 patients

Technique

1. Sterile, often helpful to anesthesize the injection area with a small needle
2. Aspirate any fluid in the joint to improve pain relief
3. Large joints: a 10-cc combination of lidocaine and steroid
4. Small joints: 1 cc to 5 cc combination of lidocaine and steroid

Efficacy

Osteoarthritis of the Knee1,2
Randomized trials have shown a significant benefit of corticosteroid injection over placebo at 1 to 3 weeks (in various studies). Using pain as an outcome measure, the benefit is not significant when studied at 6 to 12 weeks.

In one study, the presence of a joint effusion and the ability to aspirate the joint correlated with a better response to the steroid treatment.2 When comparing steroid injection to placebo, there was a significant benefit only at 1 week.

Osteoarthritis of the Hip1-2
Patients experienced a significant reduction in pain at 2 and 12 weeks; however, the effect was lost by 26 weeks.

References

1. Creamer P. Intra-articular corticosteroid treatment in osteoarthritis.Curr Opin Rheumatol.1999;11(5):417.

2. Gaffney K, Ledingham J, Perry JD. Intra-articular triamcinolone hexacetonide in knee osteoarthritis: factors influencing the clinical response.Ann Rheum Dis.1995;54:379-381.

3. Ike R. Therapeutic injection of joints and soft tissues. In:Primer on the Rheumatic Disorders.Atlanta, Ga: Arthritis Foundation; 2001.

COMPARTMENT SYNDROME

2009-07-27T06:46:00.001-07:00

Compartment syndromes develop when the pressure in closed compartment (such as the four compartments of the leg, the anterior or posterior compartment of the thigh, or the three compartments of the forearm) rises to the point that the microvascular circulation of the muscles and nerves in the compartment are compromised.

Pathophysiology

Compartment syndromes develop when the pressure in closed compartment rises to the point that the microvascular circulation of the muscles and nerves in the compartment are compromised.

Normal compartmental pressure is 0 to 10 mmHg. When the tissue pressure rises to between 10 mm Hg and 30 mm Hg of the diastolic pressure, the perfusion of both muscle and nerve is compromised and ischemia occurs.

Important things to remember:

1. With complete ischemia, muscle remains viable for up to 3 to 4 hours without irreversible damage.
1. At 6 to 8 hours of complete ischemia, there is variable recovery.
2. More than 8 hours of complete ischemia causes irreversible muscle injury.
1. Peripheral nerves show conduction changes after 1 hour of total ischemia, the neurons and supporting structures can sustain up to 4 hours of total ischemia with a reversible injury pattern (neuropraxia - conduction defect with Wallerian degeneration).

Presentation

Patients with compartment syndrome present with severe pain that is out of proportion to their injury. The evaluation of patients is difficult and deceiving as the clinical picture can be variable. The amount of pain must be assessed carefully, and assessments should be made at multiple times, ideally by the same individual or with carefully documented progress notes. Pain is often intense, and patients with a fully evolved compartment syndrome have difficulty lying quietly - most resist the clinician palpating the leg.

The key historical finding is extreme pain. Therefore, clinicians must be extremely careful not to over medicate a patient with analgesics because medications mask the compartment syndrome.

Physical Examination

5 steps of examination:

Step 1. Visually inspect the involved limb. Does the limb appear swollen? With marked swelling, the limb will often have a circular appearance and the skin may be taut and shiny without wrinkles.

Step 2. Palpate each compartment. Is there extreme pain with palpation? Is the compartment soft or hard?

Step 3. Test motor function and grade on a scale of one to five. First ask the patient to flex and extend the digits of the involved joint. This test checks if the involved muscles move easily through the compartment. If the patient can easily flex and extend, then swelling in the compartment is probably not severe. Next, test the muscle group and grade the strength.

Step 4. Passively flex and extend the digits or joint, assessing for pain. Extreme pain on passive flexion and extension is a sign of impending compartment syndrome. The tissue pressure in the compartment has risen to the point that there is severe pain with excursion of the muscle and tendons throughout the compartment.

Step 5. Test sensory nerve function by assessing sensibility of the nerves that travel through the compartment. The ability of the patient to feel light touch should be checked first and compared from side to side. If light touch cannot be felt, then one should measure the ability of the patient to detect pin prick. One should also assess for paresthesias and dysesthesias.

Assessment and Decision-Making

After examining the patient, the clinician must decide whether the patient has: 1) no evidence of a compartment syndrome, 2) a possible or probable compartment syndrome, or a 3) definite compartment syndrome.

No evidence of a compartment syndrome
In this scenario, the patient does not have pain out of proportion to injury; the involved compartment is soft, or, if swollen, the amount of swelling is in proportion to the injury; and palpation of the compartment does not produce intense pain. Motor function is normal and any weakness noted should be within the limits one would expect for normal pain and weakness secondary to the injury.

Possible or probable compartment syndrome
In this scenario, the clinician is unsure whether the patient has elevated tissue pressure, which may indicate a compartment syndrome. The patient may have any combination of pain out of proportion to injury, a tense or painful compartment, loss of motor function or sensation, or pain on passive stretch of the muscle of the compartment. To determine whether there are elevated pressures within the compartment, the clinician must measure the pressures within the compartment. Once the compartment pressures have been measured, the clinician then compares the pressures to the diastolic pressure and makes a decision as to whether a compartment syndrome is present.

Definite compartment syndrome

A definite compartment syndrome is present when the patient has severe pain out of proportion to injury, severe pain on passive stretch of the compartment and tenseness.There may be loss of neurologic function (motor or sensory changes).

The patient should be scheduled for immediate fasciotomy of the involved limb. Compartment pressures are measured to confirm the clinician's diagnosis. The pressure measurements are performed either at the bedside or in the operating room.

Tissue Pressure Measurement

Several instruments are used to measure tissue pressure. One may use a manometer, which is an electronic device such as is available in the intensive care unit, or a custom application such as the Stryker tissue pressure measurement device.

When measuring tissue pressure in a patient with a tibial fracture, the measurement should be done at the level of the fracture.

Indications for fasciotomy

The indications for fasciotomy have varied in the literature. Some authors have recommended an absolute tissue pressure measurement, while others have advocated determining the gradient by comparing the tissue pressure to either the diastolic pressure or the mean arterial pressure. The diastolic pressure is most commonly used because one does not have to do a calculation to determine mean arterial pressure (mean arterial pressure is the diastolic pressure plus one third of the difference between the systolic and diastolic pressures).

An important point to remember is that basic science studies have shown that normal muscle perfusion remains intact with tissue pressures within 10 mm Hg of the diastolic pressure. With injured muscle, the threshold decreases to within 20 mm Hg of the diastolic pressure. With this basic science knowledge, many authors now recommend fasciotomy when the tissue pressure is within 30 mm Hg of the diastolic pressure.

References

* Heckman MM, Whitesides TE Jr, Grewe SR, Judd RL, Miller M, Lawrence JH 3rd. Histologic determination of the ischemic threshold of muscle in the canine compartment syndrome model. J Orthop Trauma. 1993; 7:199-210.

* Heppenstall RB, Sapega AA, Scott R, Shenton D, Park YS, Maris J, Chance B. The compartment syndrome: An experimental and clinical study of muscular energy metabolism using phosphorus nuclear magnetic resonance spectroscopy. Clin Orthop. 1988; 226:138-155.

* Heppenstall RB, Scott R, Sapega A, Park YS, Chance B. A comparative study of the tolerance of skeletal muscle to ischemia: Tourniquet application compared with acute compartment syndrome. J Bone Joint Surg Am. 1986; 68:820-828.

* Whitesides TE, Heckman MM. Acute compartment syndrome: Update on diagnosis and treatment. J Am Acad Orthop Surg. 1996; 4:209-218.

* Whitesides TE. Compartment syndromes and the role of fasciotomy, its parameters and techniques. Instr Course Lect. 1977; 26:179-196.

Articular Cartilage

2009-07-27T06:13:00.000-07:00

Frank J. Frassica, MD

Important properties of articular cartilage include:

* Avascular (no blood vessels)
* Aneural (no nerve fibers)
* Alymphatic (no lymphatic vessels)
* Very low friction on cartilage on cartilage motion
* Self-renewing (maintenance and restoration of extracellular matrix)
* With aging, loss of ability to maintain the extracellular matrix

In regard to chondrocytes:

* By cartilage volume, the cells only represent about 1%.
* Chondrocytes are synthetic machines producing the extracellular matrix.
o Intracellular organelles
+ Endoplasmic reticulum
+ Golgi apparatus
* Chondrocytes do not have cell-to-cell contact in the extracellular matrix.
* With aging, chondrocytes lose their synthetic abilities.
* Chondrocytes respond to a number of stimuli:
o Increase matrix production after sensing degradation of the matrix
o Sense loads and increase matrix production
o Respond to growth factors and anabolic stimuli

Articular cartilage has three principal classes of macromolecules:

* Collagen – 60%
* Proteoglycans – 25% to 35%
* Noncollagenous proteins/glycoproteins – 15% to 20%

The three articular cartilage collagens that form cross bands are types II, IX, and XI.

Of particular note:

* Type XI binds to type II.
* Type IX binds to the cross-banded fibrils in the superficial layer.
* Type VI attaches to the matrix around the chondrocytes.
* Type X is near the calcified layer and is probably involved in mineralization of the calcified layer.

Noncollagenous proteins include:

* Decorin and fibromodulin bind to type II collagen and likely stabilize the type II collagen network.

Cartilage has a number of distinct zones.

The superficial zone has a number of important characteristics:

* Thinnest articular cartilage layer
* Two layers:
o Most superficial – fine collagen fibrils (lamina splendens)
o Deep layer – flattened fibroblast-like chondrocytes (parallel to joint surface)
* Forms a cartilage skin
* Important chemical properties:
o High collagen and low proteoglycan concentration
o Fibronectin and water concentrations are highest in this zone
* Great tensile stiffness and strength
* Seals off the cartilage from the immune system

The transitional zone lies between the superficial and middle zones of the articular cartilage.

The following important points should be remembered:

* The chondrocytes have a high concentration of synthetic organelles such as rough endoplasmic reticulum and Golgi apparatus.
* The collagen fibers are larger than in the superficial zone.
* The proteoglycan concentration is higher than the superficial zone.

The chondrocytes in the calcified cartilage zone show the least metabolic activity.

In contrast, the chondrocytes of the other areas are very active:

* Superficial zone
o Fine collagen fibrils (lamina splendens)
o High collagen and low proteoglycan concentration
o Fibronectin and water concentrations are highest in this zone
* Transitional zone
o The chondrocytes have a high concentration of synthetic organelles such as rough endoplasmic reticulum and Golgi apparatus.
o The collagen fibers are larger than in the superficial zone.
o The proteoglycan concentration is higher than the superficial zone.
* Middle (radial or deep) zone
o Largest diameter collagen fibrils
o Highest proteoglycan content

Other important points:

Interleukin I has the potential to increase expression of matrix metalloproteinases that can dissolve the extracellular matrix.

Type II collagen fibers resist tensile and shear deformation forces in the articular cartilage.

In contrast, the glycosaminoglycan aggregates resist articular cartilage compression and fluid flow.

Cyclic compressive loads have the ability to stimulate matrix synthesis – aggrecan core protein and the glycosaminoglycans.

The characteristic findings in osteoarthritis are:

* Asymmetric loss of the joint space
* Subchondral sclerosis and cysts
* Osteophyte formation

Osteoarthritis

As the cartilage degenerates, progressive bone remodeling occurs. The cause of osteoarthritis is unknown. From a chemical standpoint, one of the earliest findings is a decrease in the proteoglycan and an increase in the water content. One should remember:

* Constant type II collagen content
* Decreased proteoglycan concentration and decreased chain length
* Increased water content

The decreased proteoglycan content results in increased permeability of the cartilage. A reduction of the stiffness makes the articular cartilage less able to bear loads.

In the second stage, there is a cellular response – chondrocyte proliferation. Clusters of chondrocytes producing new matrix are visible.

In this stage, there is nitric oxide and interleukin I production. These are catabolic factors that increase matrix metalloproteinase activity. Degradative enzymes break down types IX and XI collagen, which may compromise the stability of the type II collagen framework.

In the last stage of osteoarthritis, there is reduced chondrocyte proliferation and function, which may be secondary to reduced ability to respond to anabolic factors (down regulation). There may be accumulation of molecules that bind to the anabolic factors (and keep the factors from the chondrocytes) such as decorin and insulin-dependent growth factor binding protein.

Bibliography

1. Mankin HJ, Grodzinsky AJ, Buckwalter JA. Articular cartilage and osteoarthritis. In: Einhorn TA, O’Keefe RJ, Buckwalter JA, eds. Orthopaedic Basic Science. 3rd ed. Rosemont, Ill: American Academy of Orthopaedic Surgeons; 2007:161-174.

Total Knee Replacement: Technique Basics

2009-07-27T05:54:00.000-07:00

Templating for Total Knee Replacement

The physical examination should include an analysis of alignment, ligamentous stability, range of motion and muscle strength and function.

These factors, coupled with a radiographic analysis, form the basis for preoperative planning.

Preoperative analysis radiographic analysis: standing anterior-posterior (AP) view, lateral view, and patellar-femoral view.

Survivorship of TKA is directly related to appropriate alignment and balance.

Surgeons should evaluate the biomechanics of knee alignment and determine the proper position of the implant on the mechanical axis. A long-standing radiograph should be obtained.

The process of establishing a femoral cut.

The distal femoral cut is not only important for maintaining varus and valgus positioning but also for maintaining the level of the joint line.

This is particularly challenging for the valgus knee in which the lateral femoral condyle is distally and posteriorly hyperplastic.

Intramedullary and extramedullary alignment guides can be used to accurately bring the distal femoral cut perpendicular to the mechanical axis in the AP plane.

Posterior condyles affect femoral rotation, especially in the valgus knee.

There are advantages of externally rotating the femoral component to approximately the epicondylar axis.

Varus Knee Management Techniques
Because varus deformity is the most common deformity in osteoarthritic knees, familiarity with medial or varus release techniques is a must for orthopedic surgeons performing TKA.

With a standard median patella approach, the first portion of a medial release is performed when the deep portion of the medial collateral ligament is released.

Some surgeons favours a subperiosteal release that does not include the pes anserinus (PES) insertion.

This release is carried posteriorly to include the semimembranous insertion on varus knees but not valgus knees.

The second portion of the release is removal of osteophytes that tent the medial collateral ligament.

With severe deformities, the posterior medial capsule must be released subperiosteally from the tibia to allow correction of the deformity.

The true medial release is performed for further correction, subperiosteally, distal to the PES insertion (but deep to the PES insertion) until the desired correction is obtained.

If medial release for a varus deformity is done in a step-wise and graded fashion, it can titrate the correction needed and allow normal ligamentous balance.

Valgus Knee Management Techniques

The valgus deformity is more complex and difficult than that done in varus knees.

Most surgeons prefer the median parapatellar incision over the median incision because this technique is easy. First, place the alignment jigs for bony cuts. Once the cuts are done, balance the soft tissues. Release the iliotibial band off Gerdy's tubercle while the lateral capsule is released from the tibia to the posterior lateral corner.

High valgus deformities require a lateral collateral ligament and popliteus, in that order, to be released from the epicondyle on the femur.

More release can be obtained by taking down the intramuscular septum and lateral gastrocnemius.

The posterior cruciate ligament plays a role in maintaining high valgus deformities.

Thus, resection of this ligament is usually required.

A lax medial collateral ligament may also contribute to this type of deformity.

References
1. Morawa MD. Templating for total knee replacement. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12- 16, 2000.
2. Reilly DT. Varus knee management techniques. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16, 2000.
3. Wright RJ. Valgus knee management techniques. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16, 2000.

Issues in Revision Total Knee Replacement

2009-07-27T05:52:00.000-07:00

Donald T. Reilly, MD. PhD

Introduction
At the recent State of the Art Update in Orthopaedics 2000 in Whistler, British Columbia, Donald T. Reilly, MD, PhD, moderated a group of presentations on issues in revision total knee arthroplasty (TKA).

Identifying Bony Landmarks in Revision Total Knee Replacement
Revision total knee replacement poses problems for the orthopedic surgeon because the loosening process destroys many anatomical landmarks. The first mutation to ascertain is that of full extension. Kenneth A. Krackow, MD, described a modification of his positioning jigs with a perpendicular marker from the femoral component with which to define full extension.

Soft tissue cannot be used as a guide for rotational alignment of the femoral component in revision surgery because the loosening process changes tissue tension, especially in the flexion space. External rotation of the femoral component closes the lateral flexion space and moves the asymmetry that is created by a perpendicular tibial cut. This femoral rotation can cause a varus or valgus malalignment in flexion. Krackow suggested using the epicondylar axis as the bony landmark to avoid excessive external rotation of the femoral component. The epicondylar axis should be ascertained independent of the bony condyles because these change dramatically in the revision setting. Soft tissue release for alignment in extension causes external rotation of the bony femur. As such, posterior bony cuts must not follow component positioning via this technique.

Tibial component rotation takes into account the (medial-lateral) M-L axis, A-P axis, and tibial tubercle. The foot is a poor landmark for tibial rotation because common deformities can significantly change its alignment. Instead, the tibial component should be matched in rotation to the femoral component in extension, with the soft tissue being used as a secondary guide for tibial orientation.

Soft Tissue Balancing on Revision Total Knee Replacement
Chitranjan S. Ranawat, MD, proposed that revision soft tissue balancing is similar to primary knee balancing. He described his method of creating medial lateral subperiosteal sleeves for exposing a stiff knee. This method releases essentially all soft tissue medially and laterally from the femur, allowing exposure of the distal femur for implantation. If there is a discrepancy in the soft tissue balancing between flexion and extension, then a constrained component is used with this exposure.

A tibial ion rod is used for the tibial cut, and axial rotation of the tibial component is deferred until the femoral component position is fixed. In revision surgery, tibial components that are smaller than the femoral component are often required. For the femoral side, Ranawat urges preservation of distal femoral bone. The joint line should be approximately 25 mm distal to the medial collateral attachment. The tibial insert should be of sufficient thickness to place tension on the soft tissue sleeve.

For valgus knees, Ranawat suggests lengthening the iliotibial band by using a "pie crust" technique with multiple stab incisions until a balanced knee is achieved. Releases should be done to allow a springiness of 2 to 4 mm in extension and 2 to 4 mm in flexion, both medially and laterally with distraction. Flexion instability is compensated for by a TC-3-type component. Ranawat emphasized the importance of wide exposure, preservation of bone with extraction, and use of modularity.

Revision of the Patellofemoral Joint
Although the patellar-femoral joint accounts for only 1% to 12% of complications in most TKA series, it causes of 40% to 50% of revisions in those series. James A. D'Antonio, MD, discussed revision resulting from patellofemoral joint problems, including fracture, loosening, pain, and instability of the patella.

D'Antonio and colleagues evaluated a series of 161 TKAs with resurfaced patella. At 5-year follow-up, the complication rate in the patellar-femoral joint was 5%. Improvement of patella complications is dependent on the cause. Prosthetic component placement, soft tissue problems, malposition of the femoral component, and design (especially metal back patellar components) are the most common causes of patella complications.

At least 5 to 6 mm of bone stock are required for surfacing in the revision setting. If less than 5 mm are available, patelloplasty must be done, according to D'Antonio. He believes that extensor malalignment should be addressed distally so that smaller bony changes can be performed. Treatment of patella fracture depends on the integrity of the extensor mechanism and whether the prosthetic patella is loose.
The series by Berry and Rand was presented, showing that patellar-femoral complications were the reason for 33% of revisions and that the revisions were subsequently associated with a relatively high complication rate. Patella-backed components should not be used.

Allograft for Bone Loss
Bone defects in the tibial plateau present technical problems in primary knee replacement surgery. However, variety of techniques are available to solve these problems. Lester S. Borden, MD, finds classification systems for bony defects such as that described by Rand[4] to be cumbersome and to lack utility in the revision setting. Borden proposed 20 mm as the size from which the differential between graft and augmentations should be decided. He stressed the importance of retaining as much cortical rim as possible and emphasized that surgeons performing revision should start with conservative bone cuts. Cancellous allograft impaction techniques can be used with cavitary defects and the component should have maximum coverage without overhang. Cancellous morsalized grafts should be avoided in segmental defects.
Whiteside[5] used morsalized cancellous allograft to fill large femoral and/or tibial defects in 63 patients (63 knees) who had revision surgery for failed arthroplasty between September 1988 and January 1993. Fourteen of the 63 revisions required yet another procedure between 3 weeks and 37 months after the revision surgery for loosening, wound avulsion, wound hematoma, painful wires, patellar tendon avulsion from the tibial tubercle, patellar subluxation, or late-onset instability.

Cement can be used for small defects that are less than 20 mm in depth and account for less than 50% of the surface area of revised tibia.[5] Lotke and colleagues[6] followed 59 patients treated with a cement fill for an average of 7.1 years. Only 1 of the fills failed, but 43 had radiolucent lines. Radiolucent lines were not correlated with clinical symptoms.

Windsor and colleagues[7] found that autograft in primary knees healed well in a series of 50 knees with defects. Wedges or blocks used for tibial defects showed the same pattern of strain[8]. The shape of the augmentation should be based on the shape of the defect.

Borden noted that although femoral bone loss is rare in primary TKA, it occurs in 25% of revisions. Grafting or augmentation to fill these defects is important to maintain the joint line. In young patients with large defects, a "tumor" type of approach should be avoided and bulk allografts should be used for stock augmentation. In summary, cavitary lesions should have cancellous grafting, and modularity has replaced the need for most bone grafts in segmental defects smaller than 20 mm.

Cases You Would Rather Refer
Joseph C. McCarthy, MD,[9] discussed particularly challenging cases in revision TKA. Poor outcomes in TKA are associated with:
• previous trauma
• previous surgery
• extensor mechanism failure
• osteoporosis
• compromised skin
• severe deformity
• neuropathic joints
• drug dependence
• morbid obesity.

McCarthy discussed postoperative reflex sympathetic dystrophy and stressed that inclusion of a pain service in treatment is very important. Loss of the extensor mechanism can be treated with allograft augmentation[10]; however, this procedure is associated with many complications, including extensor weakness and poor range of motion.

McCarthy discussed the role of Workers' Compensation in TKA. Mont and colleagues studied the influence of Workers' Compensation on the outcome of TKA in 42 patients who had been managed between January 1980 and December 1993. These patients were matched with a group of 32 patients who were not receiving compensation. After a mean time of 80 months, patients receiving compensation had a mean Knee Society score of 64 points. The patients who were not receiving compensation had a mean Knee Society score of 93 points. The difference between the two groups with regard to fair or poor results and revisions was significant (P <.01). Surgeons should be aware that Workers' Compensation is one of several variables that may have an untoward influence on the perceived outcome of total knee arthroplasty.

References
1. Krackow KA. Identifying bony landmarks in revision total knee replacement. State of the Art Update in Orthopedics 2000. Whistler, BC: February 12-16, 2000.
2. Ranawat CS. Soft tissue balancing on revision total knee replacement. State of the Art Update in Orthopedics 2000. Whistler, BC: February 12-16, 2000.
3. Antonio JA. Revision of the patellofemoral joint . State of the Art Update in Orthopedics 2000. Whistler, BC: February 12-16, 2000.
4. Rand JA. Bone deficiency in total knee arthroplasty. Use of metal wedge augmentation. 1991;271:63-71.
5. Whiteside LA, Bicalho PS. Radiologic and histologic analysis of morselized allograft in revision total knee replacement. Clin Orthop. 1998;357:149-156.
6. Lotke PA, Wong RY, Ecker ML The use of methylmethacrylate in primary total knee replacements with large tibial defects. Clin Orthop. 1991;270:288-294.
7. Windsor RE, Insall JN, Sculco TP Bone grafting of tibial defects in primary and revision total knee arthroplasty. Clin Orthop. 1986;205:132-137.
8. Fehring TK, Peindl RD, Humble RS, Harrow ME, Frick SL. Modular tibial augmentations in total knee arthroplasty. Clin Orthop. 1996;327:207-217.
9. McCarthy JC. Cases you would rather refer away. State of the Art Update in Orthopedics 2000. Whistler, BC: February 12-16, 2000.
10. Emerson RH Jr, Head WC, Malinin TI. Extensor mechanism reconstruction with an allograft after total knee arthroplasty. Clin Orthop. 1994;303:79-85.
11. Mont MA, Mayerson JA, Krackow KA, Hungerford DS. Total knee arthroplasty in patients receiving Workers' Compensation. J Bone Joint Surg Am. 1998;80:1285-1290.

Primary Total Knee Replacement: Results

2009-07-27T05:50:00.000-07:00

Donald T. Reilly, MD. PhD

Introduction
At the recent State of the Art Update in Orthopaedics 2000 in Whistler, British Columbia, James A. D'Antonio, MD, moderated a group of presentations on results of various designs in total knee arthroplasty (TKA).

Results of Porous Coated Total Knee Replacement
Lester S. Borden, MD,[1] acknowledged that cemented TKA is the "gold standard." Early designs of uncemented components were developed in an attempt to eliminate the need for cement and to prevent "cement disease." Surgeons wanted more stable bony ingrowth. Eventually "cement disease" was recognized as particle disease (mostly from polyethylene wear into crevices).
The original and most successful TKA, the porous coated anatomical (PCA) artificial total knee joints, were introduced in the early 1980s. These joints were designed for bony ingrowth and to provide for normal knee kinematics. The design also introduced modularity of the tibial components. To allow for more normal kinematics, the lack of constraint dictated a "flat-on-flat" design. This resulted in a very high rate of polyethylene wear and a revision rate of 10% per year. This design, however, contributed to the development of instrumentation for alignment of components.

Thin polyethylene, when subjected to high stresses, tends to wear excessively. This has been a major contributing factor to wear in all designs. Bartel and colleagues[2] examined polyethylene stresses in patellar components with convex-shaped articulating surfaces that contacted convex metallic surfaces. For patellar models, the von Mises stress was at or near the polyethylene yield stress in most of the contact area, which is consistent with the permanent deformation observed in many retrieved components. As such, deformation may continue, even when the component's surface has deformed and been worn into a concave shape.
Fehring and colleagues[3] evaluated 20 patients referred for pain and disability after TKA with fluoroscopy-guided radiographs. Fourteen of the 20 patients had radiolucent lines in their prostheses during this evaluation. All loose components as determined by fluoroscopy were confirmed on revision.
Fluoroscopy-guided radiographs can be helpful in evaluating the patient with a painful TKA and normal-appearing office radiographs. Newer uncemented total knee designs have improved anatomical shapes and contact areas and use screws for additional fixation. These enhancements have led to improved results with uncemented knee designs.

Results with an Hydroxyapatite-Coated Total Knee Design
Jean-Alain Epinette, MD,[4] opened by reviewing the prospective randomized analysis of Nilsson and colleagues[5] in which fixation of hydroxyapatite (HA)-coated designs in 29 knees were compared with cemented tibial components in 28 knees in the Tricon II TKA. Radiostereometric analysis revealed continuous migration of cemented components compared with slight unprogressive migration of HA-coated components. In the 40 patients (19 HA-coated, 21 cemented) remaining after 5 years, the HA-coated implants had most of their migration occurring within the initial 3 months but then stabilized, whereas the cemented implants showed an initially lower -- but over time continuously increasing -- migration.

Epinette's experience with 309 knees follow after a mean of 5 years (range 0 to 9 years) showed no mechanical failure in the femoral or tibial component. Eight of these knees required a repeated procedure for patella problems. Epinette found that HA filled in radiolucent gaps in follow-up radiographs.
Results With an All-Polyethylene Tibial Component

Evolution in TKA tibial component design has centered around metal tibial trays with improved stress transfer to the proximal tibia[6] and better fixation with pegs and cement. Benefits of metal tibial trays include durable fixation and modularity. With longer follow-up, however, polyethylene "backside" wear and osteolysis are increased.
The best data on polyethylene wear and osteolysis has been reported in the all polyethylene total condylar prosthesis,[7,8] the one piece molded metal backed IB-1 prosthesis[9] and the compression molded one piece metal backed ACG prosthesis.[10] Currently on e the AGC total knee system is being manufactured.

Chitranjan S. Ranawat, MD,[11] described his 20-year follow-up study of 220 all polyethylene total condylar prostheses. At 20-years, 20 had been revised--4 for infection, 3 for fracture, and 13 for loosening. There were no cases of osteolysis. This study presents a good case for the all-polyethylene tibial component.
Ranawat[11] also reported on a prospectively randomized 180 press-fit condylar modular versus all-polyethylene tibial components performed between 1992 and 1994. At a mean follow-up of 6 years, 5 cases in the metal-backed group underwent revision for osteolysis compared with 0 cases in the all polyethylene group (P<.05). In all cases of revision for osteolysis, there was failure of the locking mechanism and "backside" wear.

In Ranawat's opinion, improvement in the locking mechanism between the tibial polyethylene insert and the metal tibial tray is imperative to reducing the incidence of osteolysis in cemented TKA. In the meantime, he considers preferable the components of molded or newer wear-resistance polyethylene (all poly) or molded, newer polyethylene components mechanically locked during manufacture to the metal tibial tray.

Results With an Epicondylar Axis Knee
Lawrence G. Morawa, MD[12] described a retrospective analysis of 50 consecutive posterior, stabilized, demented, tricompartmental total knee replacements with a minimum follow-up of 2 years. After surgery, the average range of motion was increased from 86° to 118° flexion. All patients had improved postoperative SF-36 scores. Pain and stair climbing function improved dramatically, and there were no revisions or infections. Nonprogressive radiolucent lines were present at the cement interface of the medial tibial bone in 10% of the tibial radiographs because of sclerotic subcondyle bone. After 2 years, overall Knee Society scores were excellent in 83% and good in 17% of patients, with a mean total score of 96 points.

References
1. Borden. Results of Porous coated total knee replacement. State of the Art Update in Orthopedics 2000. Whistler, BC: February 12-16, 2000.
2. Elbert K, Bartel D, Wright T. The effect of conformity on stresses in dome-shaped polyethylene patellar components. Clin Orthop. 1995; 317:71-75.
3. Fehring TK, McAvoy G. Fluoroscopic evaluation of the painful total knee arthroplasty. Clin Orthop. 1996;331:226-233.
4. Epinette JA. Results with an HA coated total knee. State of the Art Update in Orthopedics 2000. Whistler, BC: February 12-16, 2000.
5. Nilsson KG, Karrholm J, Carlsson L, Dalen T. Hydroxyapatite coating versus cemented fixation of the tibial component in total knee arthroplasty: prospective randomized comparison of hydroxyapatite-coated and cemented tibial components with 5-year follow-up using radiostereometry. J Arthroplasty. 1999;14:9-20.
6. Bartel DL, Burstein AH, Santavicco EA, Insall JN. Performance of the tibial component in total knee replacement. J Bone Joint Surg. 1982;64A:1026-1033.
7. Ranawat CS, Boachie-Adjei O Survivorship analysis and results of total condylar knee arthroplasty. Eight- to 11-year follow-up period. Clin Orthop 1988 Jan;(226):6-13.
8. Ranawat CS, Flynn WF Jr, Deshmukh RG Impact of modern technique on long-term results of total condylar knee arthroplasty. Clin Orthop 1994 Dec;(309):131-5
9. Font-Rodriguez DE, Scuderi GR, Insall JN: Survivorship of cemented total arthroplasty. Clin Orthop, 345:79-86, 1997.
10. Ritter MA, Worland R, Saliski J. Flat-on-flat, nonconstrained compression molded polyethylene total knee replacement. Clin Orthop 321:79-85, 1995.
11. Ranawat CS. Results with an all-poly tibial component. State of the Art Update in Orthopedics 2000. Whistler, BC: February 12-16, 2000.
12. Morawa LG. Results with an epicondylar axis knee. State of the Art Update in Orthopedics 2000. Whistler, BC: February 12-16, 2000.

Complications in Total Knee Arthroplasty

2009-07-27T05:47:00.000-07:00

Donald T. Reilly, MD. PhD

Introduction

At the recent State of the Art Update in Orthopaedics 2000 in Whistler, British Columbia, Lawrence G. Morawa, MD, moderated a group of presentations centered around the diagnosis and treatment of complications in total knee arthroplasty (TKA).

Diagnosing and Treating Infection
Although infection in total knee arthroplasty (TKA) is a relatively infrequent complication, it can be devastating in terms of morbidity and cost. Lester S. Borden, MD,[1] reviewed the diagnosis and treatment of infection in TKA. He began by stressing that this is a surgical disease. Long-term antibiotic depression is rarely indicated and is generally used only in patients for whom surgery is contraindicated.

Risk factors for knee infection include:
• multiple previous infections
• history of previous infection
• inflammatory arthritis (delayed infection)
• insulin dependent diabetes
• postthrombotic syndrome
• malnutrition.

Borden reviewed the importance of perioperative antibiotics. The institutional incidence of primary TKA infection should be around 1 %. Revision total knee replacement, however, carries at least a 2-fold increased risk for infection. In addition, late infections occur in approximately 2 per 1,000 TKAs annually.

Waldman and colleagues[2] retrospectively analyzed 290 patients with TKAs performed between 1982 and 1993 to define the risk for infection associated with dental surgery.

They identified 62 TKAs with late infections (occurring more than 6 months after procedure). Seven of these late infections were temporally and bacteriologically associated with dental procedures. Eight of 9 patients received no antibiotic prophylaxis. Fifty-six percent of the patients with late infections had positive risk factors, including diabetes and rheumatoid arthritis. These authors suggested prophylaxis for extensive dental work.

Diagnosing TKA infections is challenging, and prompt diagnosis and treatment are essential for a successful outcome. Windsor and colleagues[3] found that 96% of patients with infected TKAs presented with pain and 77 % had swelling. Only 27% had fever and drainage.

Treatment options for an infected TKA include:
• antibiotic suppression alone
• aggressive wound debridement, drainage, and antibiotic suppression therapy
• resection arthroplasty
• arthrodesis
• 2-stage reimplantation
• amputation.

The definitive diagnosis of infection is recovery of neutrophils by aspiration with greater than 30,000 leukocytes, 75% of which are polymorphonuclear. Five percent of infected TKAs in the Windsor study had negative cultures.
With an established infection, suppression is suggested only for patients in which surgery is not feasible. A low-virulence-organism, secure implant components, and well-tolerated oral antibiotics are required for cases in which suppression is chosen. Debridement with retention of the implant has a greater rate of success when there is meticulous synovectomy, copious irrigation, and parenteral antibiotics for 4 to 6 weeks in cases of acute infection.

According to Borden, management of infection with arthroscopy and multiple irrigations has yielded a lower rate of success. One-stage reimplantation, a more popular approach in Europe, may be possible for patients with acutely infected cementless TKAs and allows for debridement of the prosthesis-bone interface. Reimplantation usually requires antibiotic-impregnated cement. The gold standard for treatment of TKA infection remains the 2-stage reimplantation. This is especially successful in patients with chronically infected TKAs (ie, patients in whom symptoms persist for longer than 3 weeks.

Simmons and colleagues[4] performed a meta-analysis of 77 studies of 2-stage reimplantation and found an average success rate of 80%. This technique is more successful for cases of osteoarthritis with low-virulence bacteria and less successful for cases of rheumatoid arthritics and when high-virulence bacteria or multiple-organism infections are present. According to the Backe and colleagues,[5] a second 2-stage reimplantation following a failed 2-stage reimplantation has a success rate of approximately 80%.

There are few attractive surgical options for failed treatment of infected TKA. Arthrodesis should be considered when multiple surgical attempts fail to eradicate infection. Adequate bone stock, however, must be present for arthrodesis to be successful. Knee arthrodesis is challenging surgically and can be complicated by nonunion, malunion, or recurrent infection. A modular titanium intramedullary nail has been used in an attempt to reduce the incidence of nonunion and the rate of complications.

Waldman[6] reviewed the results of knee arthrodesis after infected TKA in 21 patients with a mean age of 64 years. Patients were followed for a mean of 2.4 years, and the mean number of previous operations was 4. Solid arthrodesis was achieved in 20 of 21 patients at approximately 6 months by using an intramedullary nail.

Borden discussed his personal approach to 2-stage reimplantation. His technique includes meticulous debridement with preservation of all noninvolved bone, preservation of collateral ligaments with resection of the posterior cruciate ligament, and the use of spacers (Prostalac). Prostalac remains interesting but controversial. He stressed the importance of skin closure. In the interval between removal and reimplantation, a patient should receive 4 to 6 weeks of intravenous antibiotics and no antibiotics for 1 to 2 weeks. An erythrocyte sedimentation rate and C-reactive protein test can be used to decide whether to reimplant. Borden emphasized the importance of antibiotics in cement used for reimplantation.

Looks Good, Feels Bad
Although the rate of dissatisfaction in patients with TKA is reported to be approximately less than 1%, evaluating a patient with pain or limited function is of utmost importance. James A. D'Antonio, MD,[7] reviewed the work-up of a patient with a painful or dysfunctional TKA.

D'Antonio presented a case of a 62-year-old active man who presented with pain. Plain radiographs and an examination appeared normal. However, slight rotation in several views other than ideal positioning showed loosening of an uncemented component. It is important to obtain fluoroscopic views if perfectly tangential radiographs of the prosthesis-bone interface are not available.

The second case was a 65-year-old man who reported that his knees were not supporting him. The examination revealed a very stable, well-aligned knee with no effusion. Radiographs showed no abnormalities. The patient had a history of alcoholism, which led to D'Antonio to the conclusion that the problem was with the patient not the arthroplasty. Evaluation of a patient who is unsatisfied with their

TKA should include:

• detailed history

• detailed physical examination, including chief complaints; pain; function; and neurovascular, psychosocial, and hip examinations

• radiographs and laboratory tests.

This work-up usually yields a diagnosis before surgery is necessary. D'Antonio stressed the importance of delaying surgery until the surgeon has reached a definitive diagnosis. Patients is key for surgeons encountering the small percentage of patients with TKA who are unhappy with unexplained pain or dysfunction.

Looks Bad, Feels Good
There are many failure mechanisms in TKA. These include:

• polyethylene wear

• instability

• aseptic Loosening

• extensor mechanism dysfunction

• unexplained pain

• infection.

George D. Markovich, MD,[8] examined the issue of "silent" osteolysis and the management of bone loss in TKA.

Femoral defects distally and posteriorly can be prevented with metal blocks on the femoral component to maintain the joint line.

Tibial wedges, half block, full block, and oblique full blocks are also useful.

Stems can be used enhance fixation when augments are used or bone quality is poor.

Markovich's presented his experience with 50 revision TKAs with metal augmentation followed for a maximum of 10 years.

To date, none of his patients treated with this technique have had failure of fixation of the components.

Osteolysis due to polyethylene wear may be present in patients with few symptoms. As such, patients often do not present with symptoms until after extensive structural damage has already occurred.

Early treatment is central to the prevention of widespread bone loss.

There are few data to guide the decision to intervene.
Regardless of whether a patient has osteolysis, the surgeon should continue to focus on the goals of restoration of bone stock, reestablishment of the joint line, and recreation of stability in the revision setting.

Lonner and colleagues[9] evaluated a total of 102 revision TKAs to determine the prodromal symptoms and radiographic findings associated with failure. The most important indicator for failure was pain, occurring in 84% of patients at an average of 13 months. Radiographs underestimated the diagnosis of osteolysis to be 4%. Osteolysis was confirmed during surgery in 22% of patients. The authors recommended an annual questionnaire and weight-bearing radiographs to ensure adequate surveillance of TKA patients.

Radiographs often underestimate the extent of bone loss. This inadequacy has prompted the development of more exact techniques, such as dual-energy x-ray absorptiometry and microradiographic evaluation, into the clinical setting. These techniques, however, remain experimental. Because of the shortcomings of radiographs in diagnosing osteolysis, the surgeon needs to be prepared for more than is preoperatively visible.

Markovich briefly discussed pharmaceutical intervention to prevent osteolysis. Shanbaga and colleagues[10] evaluated oral bisphosphonate therapy in a canine total hip replacement model. The dogs were randomized into 3 groups of 8, and a right uncemented total hip replacement was done on each animal. The control group (group 1) received no particulate debris. In groups 2 and 3, a mixture of fabricated ultra-high molecular weight polyethylene, titanium alloy, and cobalt chrome alloy was introduced into the proximal femoral gap. Group 3 also received a once-daily dose of 5 mg of alendronate sodium begun on day 7 and continued until the time of sacrifice.

Radiographically, 1 of 8 control dogs and 6 of 7 dogs from group 2 had periprosthetic radiolucencies with development of endosteal scalloping. In contrast, only 1 of 8 animals from group 3 had periprosthetic radiolucencies. Tissues from both experimental groups had significant macrophage infiltration. Levels of prostaglandin E2 and interleukin-1 were also significantly higher in the experimental groups than in controls. Continuous administration of alendronate effectively inhibited bone lysis for the 24-week duration of the study. Markovich stressed, however, that the clinical usefulness of this treatment is still in question.

Unstable Total Knee Replacement
Instability is the leading cause of failure in TKA.

A patient with preoperative ligament dyslaxity requires prosthetic substitution.

In patients with a primary TKA, a knee that is unbalanced after surgery was not balanced properly during surgery.

Secondary instability after surgery may result from after delayed rupture, wear, or loosening.

Patient history and clinical findings are important in the diagnosis of instability.

Radiographs are not usually helpful. Presentation usually takes the form of dissatisfaction with the knee, multiple falls, instability, pain, and effusion.

Patients are not usually cognizant of instability and usually describe situations in which they descend ramps and their knee tends to give way. Instability must be looked for in flexion, extension, and both positions (global instability).

References
• Borden LS. Diagnosing and treating infection. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16.
• Waldman BJ, Mont MA, Hungerford DS. Total knee arthroplasty infections associated with dental procedures. Clin Orthop. 1997;343:164-72.
• Windsor RE, Bono JV. Infected total knee replacements. J Am Acad Orthop Surg. 1994 Jan;2:44-53.
• Simmons TD, Stern SH. Diagnosis and management of the infected total knee arthroplasty. Am J Knee Surg. 1996;9:99-106.
• Backe HA Jr, Wolff DA, Windsor RE. Total knee replacement infection after 2-stage reimplantation: results of subsequent 2-stage reimplantation. Clin Orthop. 1996; 331:125-31.
• Waldman BJ, Mont MA, Payman KR, et al. Infected total knee arthroplasty treated with arthrodesis using a modular nail. Clin Orthop. 1999;367:230-7.
• D'Antonio J. Looks good, feels bad. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16.
• Markovich GD. Looks bad, feels good. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16.
• Lonner JH, Siliski JM, Scott RD. Prodromes of failure in total knee arthroplasty. J Arthroplasty. 1999;14:488.
• Shanbhag AS, Hasselman CT, Rubash HE. Inhibition of wear debris mediated osteolysis in a canine total hip arthroplasty model. Clin Orthop. 1997;344:33-43.

Challenges in Total Knee Replacement

2009-07-27T05:44:00.000-07:00

Donald T. Reilly, MD. PhD

Introduction

At the recent State of the Art Update in Orthopaedics 2000 in Whistler, British Columbia, Anthony K. Hedley, MD, moderated a group of presentations on challenges in total knee arthroplasty (TKA), ranging from patellar clunk syndrome to the dislocated patella/extensor mechanism.

Patellar Clunk Syndrome

Excellent results have been reported with posterior stabilized TKA. A common complication relating to patellofemoral articulation, however, is patellar clunk syndrome. This syndrome is the painful crepitus under the quadriceps tendon at the anterior knee that is caused by soft tissue catching in the intercondylar notch of the femoral component. A fibrous nodule (hypertropic scar tissue) forms on the quadriceps tendon proximal to the patellar replacement and causes pain. George D. Markovich, MD,[1] examined the many factors involved in patellar clunk syndrome and its treatment options.

Although the cause of patellar clunk syndrome is still being determined, it probably results from a combination of implant design, patient characteristics, and surgical technique. Other issues that contribute to the development of this syndrome include notch and trochlear design, raised joint line, rotational malalignment of the tibiofemoral articulation, and superior patellar overhang.

Treatment options for the syndrome includes:
• nonsteroidal anti-inflammatory medications
• arthroscopic debridement down to the quadriceps tendon
• open synovectomy for correction of implant problems.

To prevent or reduce the incidence of patellar clunk syndrome, the implant design should be smooth from the condyles to the trochlear groove. This syndrome is more common in posterior-stabilized designs. In a prospective, randomized study, Jankiewicz and colleagues[2] found this syndrome in 2% to 3% of patients with Insall-Burstein posterior stabilized TKAs.

Lucas and colleague[3] evaluated 32 knees in 30 consecutive patients diagnosed with patellar clunk syndrome at 1 year after arthroscopic debridement through a superolateral portal. Patients were diagnosed with the syndrome an average of 12 months after their most recent knee arthroplasty. All patients treated had been free of the syndrome after surgery, although 1 patient reported persistent anterior knee pain. Knee Society scores increased from an average of 64 points to 93 points after surgery.

Exposure of the Tight Knee

Donald T. Reilly, MD, reviewed exposure of the tight knee after TKA. He emphasized the importance of the skin incision. Tight knees that have undergone several procedures often have multiple incisions. As such, a sham incision is recommended, and surgeons should include previous incisions in the current one.
Mobilization of the patella is important in the tight knee. Recreation of the medial and lateral gutters allows this mobilization. A patellar-femoral ligament release aids in exposure of the lateral knee. With severe obesity and a thickened cutaneous flap, the patella should be turned in a prepatella Bursal pocket. Exposure can be enhanced by the quadriceps snip, quadriceps turn-down, and tubercle osteotomy. Reilly stressed the importance of bone quality and fragment size (at least 6 to 7 cm in length) in the tibia tubercle osteotomy. A proximal tibial shelf should be formed to prevent migration. Various options for fixation exist, including those involving screws and wires.

The Dislocated Patella/Extensor Mechanism
Kenneth A. Krackow, MD,[5] examined patellar dislocation in TKA. According to a study by Ewald and colleagues[6] on 192 kinematic TKAs, the incidence of patella dislocation is approximately 0.65%.

There are two types of dislocation: extension and flexion. Both types of dislocation can be attributed to a weak vastus medialis oblicus. The extension type depends on the design of the prosthetic trochlear groove and valgus orientation of the femoral component. If varus is placed in the tibial cut, to obtain overall valgus alignment excessive valgus position of the femoral component (increased Q angle) occurs and capture of the patella in extension is made difficult. Because it is mostly a dynamic muscular balance problem, extension-type dislocation is difficult to detect in surgery and can be impossible to detect in a paralyzed patient.
Flexion is the more common type of dislocation. It too is exacerbated by an increased Q angle. Other causes of flexion are overstuffing of the patellar-femoral joint, femoral component malrotation, poor capture in congruent design-type components, and a poorly done patella bony cut.
Minor subluxation can be treated with valgus release but complete dislocation usually requires tibial tubercle medialization without distallization. Krackow described his personal experience of 22 knees in 19 patients in which tibial tubercle medialization corrected dislocation of the patella.

References
1. Markovich GD. Patellar clunk syndrome. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16.2. Jankiewicz JJ. A prospective, randomized study of patellofemoral complications in two posterior cruciate-substituting total knee systems. Eastern Orthopaedic Association Meeting; 1995.
2. Lucas TS, DeLuca PF, Nazarian DG, Bartolozzi AR, Booth RE Jr. Arthroscopic treatment of patellar clunk. Clin Orthop. 1999;367:226-9.
3. Reilly DT. Exposure of the tight knee. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16, 2000.
4. Krackow KA. The dislocated patella/extensor mechanism. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16, 2000.
5. Wright J, Ewald FC, Walker PS, Thomas WH, Poss R, Sledge CB. Total knee arthroplasty with the kinematic prosthesis. Results after five to nine years: a follow-up note. J Bone Joint Surg Am .1990;Aug;72:1003-1009.

Basic Science Issues in Primary Total Knee Replacement

2009-07-27T05:36:00.000-07:00

Donald T. Reilly, MD. PhD

Introduction

At the recent State of the Art Update in Orthopaedics 2000 in Whistler, British Columbia, Kenneth A. Krakow, MD, moderated a group of presentations on the anatomy and biomechanics of total knee arthroplasty (TKA).

Anatomy and Biomechanics of the Normal Knee

Donald T. Reilly, MD, PhD,[1] explained the importance of incorporating normal knee kinematics into total knee designs. The historical anatomical orthogonal approach to knee kinematics induces the "J-curve," or the instant center of rotation of the knee. Brunet and colleagues[2] have demonstrated that analysis using the mechanical axis to orient the plane of rotation produces a signal point that defines the instant center of rotation as the epicondylar axis. This simplifies prosthetic design because a single radius can be used in the prosthesis for flexion and extension of the knee. This also simplifies manufacture and may eliminate mid-flexion instability. Designs based on the "J-curve" would be expected to produce better kinematics if placed in anatomical position rather than in the externally rotated femoral position. With a single axis of rotation kept more posterior, the momentum for the extension mechanism is enhanced and stair climbing and rising from a chair may be improved.

Biological Analysis of Retrieved Total Knee Arthroplasties
Thomas W. Bauer, MD, PhD,[3] discussed the benefits of analyzing retrieved TKAs. Retrieval analysis allows investigators to determine whether the design goals of the arthroplasty have been met in the clinical setting. Bauer first described levels of ingrowth in uncemented knees. Ingrowth has been shown in the past to occur in 10% to 29% of uncemented tibiae. Dr. Bauer presented retrieval data from a 59-year-old woman with rheumatoid arthritis who died subsequent to a well-functioning TKA. The analysis for ingrowth with both coronal and sagittal sections of the specimen showed less than 5% ingrowth of the entire surface area. This small amount of bony ingrowth implies that channels allow debris to contact the bone-prosthesis interface and cause osteolysis.
In retrieval studies, differentiation between wear and deformation is difficult. Bauer presented his own analysis of "backside wear" on 105 retrieved tibial inserts of multiple designs.[3] A total of 22 inserts showed evidence of backside wear, whereas many more showed evidence of deformation. However, creep cannot be considered as wear. Thirty-one inserts showed eccentric patterns of wear; these patterns were more common in retained typed replacements of the posterior cruciate ligament. Bauer pointed out that the retrievals were from revisions and not necessarily from well-functioning total knee replacements. The high backside wear was attributed to thin polyethylene, high articular surface wear, and length of time in vivo. These studies question the clinical significance of backside wear.
Does Contact Area Matter?
Traditionally, TKA designs have focused on increasing surface area of contact to decrease stresses at the articulation. Avram A. Edidin, PhD,[4] challenged the dictum that contact area is the all-important variable in TKA wear.
Retrieved degraded tibial components have the appearance of "case-hardened failure," in which the predominant failure mechanisms are spalling and galling. These failure mechanisms result more from degradation than from stress. To investigate these mechanisms, Edidin developed a small punch test that causes multiaxial loading similar to that which occurs in the polyethylene of TKAs. This test can retrieve small specimens throughout the thickness of a polyethylene insert and shows that degraded areas occur in the subsurface region where stresses (regardless of conformity) are highest. Sterilization of the material in inert atmospheres decreases degradation and enhances resistance to stresses. These experiments postulate that degradation rather than stress is the primary reason for delamination in TKA.

Osteotomy-Unicondylar Replacement

Peter M. Bonutti, MD,[5] outlined the complexities facing orthopedic surgeons choosing the best procedure for TKA in patients with unicompartmental osteoarthritis. Tibial osteotomy is favored for the younger, highly active patient with good range of motion and a normal patellar-femoral joint. Contraindications to this procedure include multiple compartment involvement and inflammatory disease. Unless a closing wedge procedure is prevented by ligament laxity, Bonutti favors this procedure over the opening wedge procedure because of the higher complication rate secondary to device failure and graft collapse in the open wedge procedure. Although osteotomy has poor long-term results, it can "buy time" for younger patients to perform more strenuous activities and postpone the need for arthroplasty.
The ideal patient for unicondylar replacement is an older, thinner patient with good range of motion and lower activity levels. This type of arthroplasty requires adequate function of all ligaments and minimal deformity to achieve the highest success rate. Disadvantages of the procedure include the small number of patients who fulfill this criteria and the resulting lack of experience with the procedure for orthopedic surgeons coupled its level of difficulty.
TKA remains the gold standard for elderly patients. This procedure yields the most reliable pain relief and longevity in patients with full compartment involvement, poor range of motion, ligament instability, and severe deformity.

References
1. Reilly DT. Anatomy and biomechanics of the normal knee. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16, 2000.
2. Brunet ME, Kester MA, Cook SD, Haddad RJ, Skinner HB. Determination of the transverse centre of rotation of the knee using CAT scans. Eng Med. 1986;15:143-7.
3. Bauer TW. Biological analysis of retrieved total knees. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16, 2000.
4. Edidin AA. Does contact area matter? State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16, 2000.
5. Bonutti PM. Osteotomy-unicondylar replacement-total knee replacement. State of the Art Update in Orthopaedics 2000. Whistler, BC: February 12-16, 2000.

Your attitude changes your reality.

2009-06-26T10:14:00.000-07:00

We have all heard that you should keep a positive attitude or perhaps that “you need to change your attitude!”. That is a nice piece of advice I suppose, but without any more reasons to do it is very easy to just brush such suggestions off and continue using your old attitude.

But the thing that I’ve discovered the last few years is that if you change your attitude, you actually change your reality. When you for instance use a positive attitude instead of a negative one you start to see things and viewpoints that were invisible to you before. You may think to yourself “why haven’t I thought about things this way before?”.

When you change your attitude you change what you focus on. And all things in your world can now be seen in a different light.

This is of course very similar to the previous tip but I wanted to give this one some space. Because changing your attitude can create an insane change in your world. It might not look like it if you just think about it though. Pessimism might seem like realism. But that is mostly because your R.A.S is tuned into seeing all the negative things you want to see. And that makes you “right” a lot of the time. And perhaps that is what you want. On the other hand, there are more fun things than being right all the time.

If you try changing your attitude for real – instead of analysing such a concept in your mind - you’ll be surprised.

You may want to read more about this topic in Take the Positivity Challenge!

Mistakes and failures are good.

2009-06-26T10:11:00.000-07:00

When you are young you just try things and fail until you learn. As you grow a bit older, you learn from - for example - school to not make mistakes. And you try less and less things.

This may cause you to stop being proactive and to fall into a habit of being reactive, of waiting for someone else to do something. I mean, what if you actually tried something and failed? Perhaps people would laugh at you?

Perhaps they would. But when you experience that you soon realize that it is seldom the end of the world. And a lot of the time people don’t care that much. They have their own challenges and lives to worry about.

And success in life often comes from not giving up despite mistakes and failure. It comes from being persistent.

When you first learn to ride your bike you may fall over and over. Bruise a knee and cry a bit. But you get up, brush yourself off and get on the saddle again. And eventually you learn how to ride a bike. If you can just reconnect to your 5 year old self and do things that way - instead of giving up after a try/failure or two as grown-ups often do – you would probably experience a lot more interesting things, learn valuable lessons and have quite a bit more success.

Don’t beat yourself up.

Why do people give up after just few mistakes or failures? Well, I think one big reason is because they beat themselves up way too much. But it’s a kinda pointless habit. It only creates additional and unnecessary pain inside you and wastes your precious time. It’s best to try to drop this habit as much as you can.

A 3-Year-Old Girl With Fever and a Limp

2009-06-25T22:56:00.001-07:00

Background

3-year-old girl is brought to the emergency department (ED) by her parents with a fever and refusal to walk secondary to pain in her right leg. The pain is associated with thigh and back pain on the same side as the limp. The day before presentation, the child's mother picked her up from her babysitter, where she noticed that the child was irritable and crying. At that time, the child was pointing at and trying to touch her back, and she was walking with a noticeable limp. The parents called the patient's pediatrician, who recommended an antipyretic with follow-up the next day. The review of symptoms is only remarkable for a 1-week history of a "cold" with a runny nose and a cough. The mother denies any history of trauma to the affected extremity, and there is no prior history of similar problems. The patient's past medical history is unremarkable. The child is well-appearing and has been regularly observed by the outpatient pediatric department. The patient's immunization schedule is up to date. The child's developmental milestones are appropriate for her age. The family history is noncontributory.

On physical examination, the patient's vital signs are stable, with a blood pressure of 103/66 mm Hg, pulse rate of 115 bpm, respiratory rate of 24 breaths/min, and an oxygen saturation of 100% while breathing room air. Her temperature is 97.5°F (36.4°C).The patient initially refuses to bear weight on the right leg and is unwilling to walk. She is tearful and uncooperative as a result of the pain. The respiratory and cardiac portions of the physical examination are normal. The abdominal examination is also normal, with no palpable masses or tenderness to deep palpation. There is localized exquisite tenderness over the L1-2 region of the back, with slight induration noted in the overlying tissue. The lower extremities are well-perfused, with intact peripheral pulses; no external evidence of trauma is found. There is no limitation in the range of motion at the hip and knee joints bilaterally, with unremarkable obturator and psoas signs. The neurologic examination is normal. No lymphadenopathy is detected.

The initial laboratory investigations reveal an elevated white blood cell (WBC) count of 20.5 × 10³/μL (20.5 × 10⁹/L; neutrophils, 66.5% [0.66]; lymphocytes, 21% [0.21]; monocytes, 11.3% [0.11]), an elevated erythrocyte sedimentation rate of 87 mm/h, a C-reactive protein (CRP) level of 49.5 mg/L, a creatine kinase of 69 units/L (69 U/L), and a lactate dehydrogenase of 247 units/L (247 U/L). The urinalysis is normal, with no evidence of infection or hematuria. Plain radiographs of the lumbar spine are obtained (see Figures 1 and 2) and are essentially unremarkable. Since there is a high suspicion for serious pathology based on the clinical presentation and the results of the laboratory investigations, urgent magnetic resonance imaging (MRI) scans of the spine are also obtained (see Figures 3 and 4).

Figure 1. (Click to enlarge)	Figure 2. (Click to enlarge)
Figure 3. (Click to enlarge)	Figure 4. (Click to enlarge)

Question

What diagnosis do the findings on the MRI scan suggest?

Psoas abscess

Spinal epidural abscess

Retroperitoneal schwannoma

Retroperitoneal hematoma

Please try to answer first before you scroll down

Hint: Look closely at the area of the psoas muscle.

Answer

		Your Colleagues Responded:
Psoas abscess	Correct Answer	70%
Spinal epidural abscess		14%
Retroperitoneal schwannoma		6%
Retroperitoneal hematoma		8%

Discussion

As previously mentioned, the lumbosacral plain films were essentially unrevealing (see Figures 1 and 2). The MRI scan of the lumbosacral region, however, revealed a right multiloculated psoas abscess, with paraspinal extension in the region of L3-4 (see Figures 3 and 4) and possible involvement of the ipsilateral pedicle of L3 (not shown in the images provided). Osteomyelitis could not be ruled out based on the images. The abscess measured 1.1×0.6×2.5 cm.

A psoas abscess may be classified as primary or secondary, depending on the presence or absence of an underlying cause. In cases of primary psoas abscess, there is no identifiable source of infection. The psoas muscle is a single structure ("psoas major") in 70% of people, but the remaining 30% also have a smaller "psoas minor", which lies anterior to the psoas major and along the same course. In the lower half of the psoas muscle's course, it runs alongside the iliacus muscle, with a common tendon insertion into the lesser trochanter. Together, they are referred to as the iliopsoas. It lies in close proximity to many organs, such as the sigmoid colon, jejunum, appendix, ureters, aorta, renal pelvis, pancreas, iliac lymph nodes, and the spine. Infections in these organs can contiguously spread to the psoas muscle. A rich vascular supply is believed to predispose it to hematogenous spread from sites of occult infection.^[2,3,5,7]

A psoas abscess in children classically presents as a triad of fever, limp, and hip pain. It is important to differentiate between primary disease of the hip and a psoas abscess, as close proximity of a psoas abscess to the hip capsule can result in a similar presentation. This contributes to its extreme clinical variability. Passive rotation of the hip joint in flexion is possible in cases of psoas abscess, whereas in primary disease of the hip, resistance would be likely. Dysfunction of this joint, however, is extremely variable, ranging from complete pseudoparalysis to normal range of motion. In our case, the child presented with the additional finding of tenderness localized to the lower back, which led to an initial incorrect working diagnosis of diskitis. The differential diagnoses in this patient included psoas abscess, pyelonephritis (ruled out by the urine analysis), osteomyelitis, and a neoplastic process. Garner et al has suggested that the incidence of psoas abscess is probably underreported.^[11] Primary psoas abscess has a better prognosis than secondary psoas abscess, with a mortality rate of 2.4% (18.9% for secondary abscesses). The median time of diagnosis is 3 days, and the median hospital stay is 27 days. The major cause of death is delayed or inadequate therapy.^[6,13,14]

The appropriate imaging studies are important to accurately diagnose this uncommon clinical presentation. Ultrasonography has been recognized as the quickest and least expensive diagnostic imaging modality, as well as being a safe one. It can also differentiate between solids and liquids but, unfortunately, has a low sensitivity. Plain films of the abdomen may show enlargement or loss of definition of the psoas muscle or gas shadows in the soft tissue. Even though findings on plain films correlate poorly with a lesion, especially given the frequent presence of overlying bowel and stool, studies have shown that plain films should be performed before other imaging modalities in patients with suspected psoas abscesses (but may not be necessary if a computed tomography [CT] scan is already planned). CT scans done with intravenous (IV) contrast will show rim-enhancing hypodense areas, with secondary findings of inflammation obliterating surrounding tissue, gas bubbles, and bone destruction when present. There may be marked wall thickening, rim thickening, or multiple cavities, which suggest tuberculous rather than pyogenic infection. CT scans are also useful in recognizing potential etiologies such as Crohn disease and appendicitis. MRI (which was the diagnostic study in this case) has been reported to be more sensitive than CT scanning in displaying tissue contrast resolution and in screening out bone interference, as well as showing the extent of disease. A study by Yin et al recommended the use of a bone scan, especially in patients presenting with low back pain and an established fever of unknown origin, as it allows detection of unexpected concomitant infections.^[1,2,3,4,10]

A review of the literature published from 1881 through 1990 revealed that the incidence of psoas abscesses approximates 4 cases per 100,000 population per year, with a more recent Taiwanese study reporting that the rate of occurrence was 2.5 cases annually.^[4] These incidences reflect adult patients. In Asia and Africa, 99.5% of all psoas abscesses are primary, compared with 61% in the United States and Canada and 18.7% in Europe. The causes of psoas abscess in the Western world have changed since the beginning of the 20th century. Primary psoas abscesses caused by hematogenous spread from an occult source is common, especially in immunocompromised individuals.

In the past, psoas abscess was mainly caused by tuberculosis of the spine (Pott disease), but with the decline in the prevalence of infections caused by Mycobacterium tuberculosis, major pathogens associated with psoas abscesses are those related to diseases of the digestive tract. This is reflective of the role of contiguous sites of infection in the development of a psoas abscess. Common secondary causes of psoas abscess include Crohn disease (60%), appendicitis (16%), ulcerative colitis, diverticulitis, colon cancer (11%), and vertebral osteomyelitis (10%). In secondary psoas abscesses, cultures are often mixed with Escherichia coli and BacteriodesStaphylococcus aureus is the most common isolated organism in primary disease. Leukocytosis is the most common laboratory finding.^[2,3,7,9] species predominating.

Without localizing tenderness, the presentation of fever and irritable hip could be attributed to primary diseases of the hip and, therefore, it is important that the clinician know how to distinguish between psoas abscesses and primary hip diseases. In psoas abscess, the posterior part of the hip joint is not tender, and a fully flexed hip can be rotated without pain; this would be difficult in patients with hip problems. Digital rectal examinations produce tenderness in psoas muscle disease.

Percutaneous drainage and antibiotics are the first line of treatment, but there is a high recurrence rate. In the past, open drainage of the abscess through a McBurney or iliac crest incision was performed. Open surgical drainage allows simultaneous treatment of the underlying pathology in secondary abscess. The duration of antibiotic therapy must be individualized and graded by the clinical signs and any involvement of other sites.^{[2,6,8,11,13]}

The patient in this case was started on empiric intravenous antibiotic therapy, initially on ceftriaxone 75mg/kg/day. An ultrasonogram obtained shortly after admission was read as a "negative study of the upper abdomen, perirenal and perivertebral lower thoracic lumbar area". Following consultation with the infectious disease service, the antibiotic regimen was changed to cefepime to provide better broad-spectrum coverage. A review of the MRI findings with the interventional radiology department led to the decision that an invasive drainage procedure for a relatively small collection would not be immediately warranted, and a "wait-and-see" approach to determine the response to the intravenous antibiotics would be the best course of action. After 3 days of intravenous antibiotic therapy, the child's fever subsided, and she was noted to be moving around without limping and with no residual tenderness on examination. If fact, her mother described her as "back to her old self." A consultation with the neurology service found no neurologic deficits, and the initial limp was attributed to pain. A repeat CRP level was obtained, with a result of 34.5mg/L. The final results of the blood and urine cultures, as well as a purified protein derivative (PPD), were all negative.

As the child was doing well clinically (running and jumping up and down) and had a compliant parent, the patient was discharged on hospital day 5 with a combination antibiotic regimen of rifampin and amoxicillin/clavulanic acid for 4 weeks, along with appropriate outpatient follow-up with her primary pediatrician and an infectious disease specialist. Repeat MRI scans performed at 1 month and again at 3 months after discharge demonstrated complete resolution of the collections, except for a residual "abnormal signal intensity in the right pedicle of L3", which persisted with no identifiable clinical impact; the patient was noted to have complete resolution of her symptoms. It should be noted that the use of IV antibiotics as the sole modality of therapy in our case was unusual for the management of a psoas abscesses.

Questions

Which of the following statements about psoas abscess imaging is true?

MRI has been reported to be more sensitive than CT scanning

Ultrasonography is more sensitive than CT

A negative plain film of the area can rule out psoas abscess

CT scanning is the least expensive and quickest imaging modality

Which of the following statements about the psoas muscle's anatomy is true?

The psoas muscle together with the iliacus muscle is referred to as the iliopsoas.

Seventy percent of individuals have a smaller secondary psoas muscle.

The psoas muscle is relatively isolated from other organs.

A poor vascular supply can cause hematogenous spread from sites of occult infection.

Please try to answer first before you scroll down

Answer

Which of the following statements about psoas abscess imaging is true?

		Your Colleagues Responded:
MRI has been reported to be more sensitive than CT scanning	Correct Answer	86%
Ultrasonography is more sensitive than CT		4%
A negative plain film of the area can rule out psoas abscess		2%
CT scanning is the least expensive and quickest imaging modality		6%

Which of the following statements about the psoas muscle's anatomy is true?

		Your Colleagues Responded:
The psoas muscle together with the iliacus muscle is referred to as the iliopsoas.	Correct Answer	84%
Seventy percent of individuals have a smaller secondary psoas muscle.		5%
The psoas muscle is relatively isolated from other organs.		5%
A poor vascular supply can cause hematogenous spread from sites of occult infection.		5%

The psoas muscle is a single structure ("psoas major") in 70% of people, but the remaining 30% also have a smaller "psoas minor", which lies anterior to the psoas major and along the same course. In the lower half of the psoas minor's course, it runs alongside the iliacus muscle, with a common tendon insertion into the lesser trochanter. Together, they are referred to as the iliopsoas. It lies in close proximity to many organs, such as the sigmoid colon, jejunum, appendix, ureters, aorta, renal pelvis, pancreas, iliac lymph nodes, and the spine. Infections in these organs can contiguously spread to the psoas muscle. A rich vascular supply is believed to predispose it to hematogenous spread from sites of occult infection.

			Source: http://cme.medscape.com