Preoperative tibiofemoral angle predicts survival of proximal tibia osteotomy.

A prospective group study was done to clarify whether perioperative variables such as preoperative and postoperative tibiofemoral angles influence the survivorship of proximal tibia osteotomy as measured by conversion to arthroplasty and patient dissatisfaction. The results of 93 proximal tibial osteotomies in 82 consecutive patients with medial compartment osteoarthrosis were followed up for a mean of 10.9 years. All data were analyzed by the Kaplan-Meier survivorship method and the multivariate Cox proportional hazards model. Only the preoperative tibiofemoral angle was a predictor of conversion to arthroplasty and patient dissatisfaction. The ideal prognostic cutoff angle was 9 degrees or less varus. Increasing the preoperative varus alignment 1 degrees would result in a 1.2 (95% confidence intervals, 1.02-1.50) times higher risk of conversion to a total knee arthroplasty and a 1.5 (95% confidence intervals, 1.27-1.76) times higher chance of patient dissatisfaction. Factors such as age, gender, body mass index, Ahlback's classification, and postoperative tibiofemoral angle were not significant. We think that proximal tibial osteotomy should be considered for patients with medial compartment osteoarthrosis and a preoperative varus alignment of 9 degrees or less, whereas arthroplasty is a more suitable alternative for patients with preoperative varus alignment greater than 9 degrees.