Abstract
Background: To perform a medial open-wedge high tibial osteotomy (OWHTO), surgeons frequently expose the medial-proximal tibia by partial or complete distal release of the overlying insertion of the superficial layer of the medial collateral ligament (sMCL). Biomechanically, the sMCL is the primary restraint to valgus forces. Therefore, any release of the sMCL can lead to valgus instability of the knee joint. The purpose of this study was to clarify the valgus instability after the release of the distal attachment of the sMCL in OWHTO.
Methods: Between 2009 and 2015, 84 consecutive patients (93 knees) who underwent OWHTO using a locking plate were enrolled in this study. There were 19 men and 65 women with a mean age of 60 years (range; 20 to 78 years) at the time of surgery. We performed the complete release of the distal attachment of the sMCL. Then, a biplanar osteotomy of the tibia was performed. A beta-TCP spacer was implanted in the opening space. Then, a locking plate was implanted onto the tibia. All patients underwent clinical and radiological examinations preoperatively and at one year postoperatively. To assess objective medial instability, joint line convergence angle (JLCA) and the medial joint space (MJS) were evaluated.
Results: Postoperatively, the mean Japan Orthopaedic Association score significantly improved from 69 to 90 points (total score: 100 points, P<0.0001). The JLCA and MJS significantly increased immediately after the release of the distal attachment of the sMCL intraoperatively (6.7° and 11.4 mm, P<0.0001). However, there were no significant differences in the JLCA and MJS between preoperative (0.4° and 6.7 mm) and one-year postoperative evaluations (0.4° and 6.3 mm).
Conclusion: The complete release of the sMCL did not cause postoperative valgus instability at one year after OWHTO procedure.
