Laxity after complete release of the medial collateral ligament in primary total knee arthroplasty

Medial collateral ligament (MCL) release is one of the essential steps toward the achievement of ligament balancing during the total knee arthroplasty (TKA) in patients with varus deformity. When the varus deformity is severe, complete release of the MCL until balanced is often required. However, it is believed that complete MCL release may lead to catastrophic laxity. The purpose of this prospective study is to compare the medial joint gap opening in postoperative valgus stress radiograph in patients with complete MCL release against patients with partial release.

Out of 209 primary TKAs performed for degenerative osteoarthritis, complete MCL release was required in 33 cases (group I) by sub-periosteal detachment at proximal tibia using periosteal elevator. For the remaining 176 knees (group II), partial release of MCL was done. At postoperative 6 months and 1 year, both groups were evaluated for comparing the joint gap on valgus stress radiographs using modified Telos device in 0°, 45°, and 90° of flexion. Additional parameters which were analyzed included preoperative varus and valgus stress radiographs in full extension and pre- and postoperative mechanical alignment in each group. The knee range of motion (ROM) and clinical scores were evaluated at 1-year follow-up.

The mean values of the joint opening on the postoperative valgus stress test with the knee joint extended, and in the 45° and 90° flexed states at 6 months and at 1 year postoperatively in group I were not statistically significantly different from those of group II. The clinical scores also did not show a statistically significant difference between two groups. There was a statistically significant difference in ROM between two groups, pre- and postoperatively and the difference was 5°, respectively.

This study suggests that complete MCL release for ligament balancing is a safe procedure and does not lead to postoperative laxity.