Abstract
Chronic ligament insufficiency in total knee arthroplasty is associated with extension/flexion imbalance, late rupture of the posterior cruciate ligament (PCL), excessive joint line elevation and PCL insufficiency.
To solve the ligament balance problem, designated anatomical ‘cookbook’ bone cuts are used. Cutting ligaments affects flexion and extension gaps differently, and saving the PCL makes flexion gap adjustment difficult.
In ligamentous releases, the extension gap is affected by release of pes tendons, semimembranosus, iliotibial tract, biceps tendon, gastrocnemius tendon, and popliteus. Extension and flexion gaps are affected by release of the medial and lateral capsular ligaments, superficial medial collateral ligament, and lateral collateral ligament. The 50% rule states that flexion increases 50% more than extension with release.
Revision of all implants is usually needed. A liner exchange seldom works. Flexion/extension balance remains the critical problem. Modular revision implants are critical for correction of the gaps.
The abstracts were prepared by Professor M. B. E. Sweet. Correspondence should be addressed to him at The Department of Orthopaedic Surgery, Medical School, University of Witwatersrand, 7 York Road, Parktown, Johannesburg, 2193 South Africa
