Challenges in Total Knee Replacement

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.