Factors affecting functional medial ligament balancing in patients undergoing total knee arthroplasty for varus knees

Background: We investigated factors affecting the degree of medial ligament release necessary for equal medial/lateral ligament balancing in patients undergoing total knee arthroplasty (TKA). Methods: This study enrolled 112 patients (129 knees) who underwent TKA due to medial compartment knee osteoarthritis (OA) with varus deformity. The procedure for medial ligament release was divided into 3 steps, based on an original algorithm, and the associations between preoperative patient characteristics and release steps necessary for appropriate balancing was analyzed. Results: The data showed that degree of medial release was proportional to preoperative femorotibial angle (FTA), whereas neither preoperative range of motion nor preoperative flexion angle was associated with medial ligament release. Correction of larger flexion contracture required more-advanced steps of medial ligament release. Severity of OA findings on radiographic classification was not associated with the degree of medial release intraoperatively. The results indicate that release of posterior oblique fibers and the posterior capsule was more important than release of anterior longitudinal fibers in achieving significant alleviation of preoperative flexion contracture with a posterior-stabilized prosthesis. Conclusions: The FTA the presence of flexion contracture affected the site and degree of medial ligament release in patients undergoing TKA for varus knees.