MEDIAL RELEASE TECHNIQUES IN TOTAL KNEE ARTHROPLASTY: OUTCOME AND RATIONALE

Abstract

Introduction: During total knee arthroplasty (TKA), release of the medial structures is often required in the varus knee to obtain adequate ligamentous balancing. The aim of this study is to investigate the

1. clinical outcome,

2. ligamentous stability and

3. alignment after application of the various medial release techniques (capsular release and deep MCL, pie crust of superficial MCL, superficial MCL release on the tibial side, release of semimembranosus tendon) and

4. to propose a rationale for their use.

Materials and Methods: Between January 2000 and December 2004, 359 patients underwent a cemented posterostabilized TKA with a third condylar design (HLS prosthesis, Tornier, Grenoble, France) for primary unilateral varus osteoarthritis. One hundred twenty eight male and 231 female patients patients wer operated on at a mean age of 71 years. All patients were evaluated preoperatively and at 3 months, 6 months and 12 months postoperative.

In 255 of the 359 (71%) primary TKA’s, symmetrical gaps could be achieved by releasing the capsula and the deep MCL (group 0). In 87 cases (24%), an additional piecrust of the superficial MCL was necessary (group 1). In 55 cases out of these 87 an additional release of the insertion of the semimembranosus was performed. In 17 out of the 359 (5%), the medial tightness necessitated a distal release of the superficial MCL (group 2).

Results: All knees improved significantly postoperatively both in pain and function. Overall mean flexion at 12 months was 122 degrees.

The mean preoperative mechanical femorotibial angle (MFTA) was 174.0, 172.1 and 169.5 and was corrected postoperatively to 179.1, 179.2 and 177.6 for group 0, 1 and 2 respectively.

At 12 months, mediolateral stability was clinically evaluated as normal in 97% for group 0, 95% for group 1 and 83% for group 2. Three percent (3%), 5% and 17% has a mediolateral laxity ranging from 6–9 degrees for group 0,1 and 2, respectively.

Conclusion: Based on these results, the authors propose the following rationale: the capsule and deep MCL should always be released. In varus knees < 8°, a pie crust of the superficial MCL can be associated. In a varus knee between 8 and 10°, a release of the MCL on the tibial side is indicated. A release of the semimembranosus tendon can be associated for fixed flexion contracture. Pie crust of the MCL is a safe and reliable release technique and is able to selectively address the posterior and/or anterior fibers of the superficial MCL.