Does Superficial Medial Collateral Ligament Release in Open-Wedge High Tibial Osteotomy for Varus Osteoarthritic Knees Increase Valgus Laxity?

Abstract

Medial open-wedge high tibial osteotomy (OWHTO) requires the release of the superficial medial collateral ligament (sMCL). However, research on medial laxity among patients who undergo OWHTO is rare. To evaluate the changes in medial laxity of the knee joint as related to the complete release of the sMCL through serial valgus stress radiographs in patients who underwent OWHTO. Cohort study; Level of evidence, 2. A total of 48 patients (54 knees) who received OWHTO and were followed for more than a year and for whom serial valgus stress radiography data were available were retrospectively reviewed. To assess the medial laxity of knee joint, medial joint space opening (MJO) was measured while valgus stress of 15 kgf was loaded on the knee joint. The MJO was measured before surgery, during surgery before release of the sMCL under anesthesia, after the release, and after fixing with a TomoFix plate following the opening of the osteotomy site, as well as 3, 6, and 12 months after surgery. Serially measured MJOs were analyzed to evaluate the changes of medial laxity. The MJO significantly increased after the release of the sMCL (mean ± SD, 12.2 ± 1.2 mm) compared with before the release (9.0 ± 1.1 mm) (P < .001). The MJO measured after fixing with the TomoFix plate following the opening of the osteotomy site (9.2 ± 1.2 mm) was significantly decreased compared with that measured after the release of the sMCL and was not significantly different from the MJO measured before release of the sMCL. No significant difference was observed among MJOs that were measured 3, 6, and 12 months after surgery. Comparison of MJOs before and after surgery also showed no significant differences. Complete release of the sMCL during OWHTO increases the MJO. However, the MJO decreased to the level before sMCL release after fixing with the TomoFix plate following the opening of the osteotomy site. Medial laxity induced by the complete release of the sMCL can be recovered by opening the osteotomy site.