Total Knee Replacement: Technique Basics

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.