Long-term survival and predictors of failure of opening wedge high tibial osteotomy.

Background: The primary aim was to evaluate the long-term survival of opening wedge high tibial osteotomy (HTO) for isolated osteoarthritis in the medial compartment of the knee. The secondary objective was to identify independent predictors of conversion to total knee arthroplasty (TKA). Methods Two-hundred forty-seven consecutive cases of open wedge HTO performed at the study centre were retrospectively analysed. Mean age at the operation was 42,8 years (range 15–70) and most patients were male (70%). Mean follow-up was 11.6 years (6–17). Failure was defined as conversion to TKA. Kaplan–Meier and Cox regression analyses were performed. Results Thirty-three of the 247 HTOs (13.4%) were converted to knee replacement, with 86.6% of the original procedures surviving at a mean 12-year follow-up. Kaplan-Meier survival estimates at 17 years for HTO were 75.5% (95% confidence interval [CI] 66.7–84.3). There was significant difference ( p  < 0.001) in the 17-year survival rate between obese (55.5%; 95% CI 35.3–75.6) and non-obese (79.7%; 95% CI 70.1–89.2) patients. The determinants of conversion to knee arthroplasty detected at multivariate Cox regression analysis were Body Mass Index, severity of cartilage degeneration in the medial compartment (Outerbridge grade), and age. Conclusions The long-term survival of open wedge HTO for osteoarthritis in the medial compartment of the knee is satisfactory. The risk of conversion to TKA is significantly increased in obese patients. Advanced age and severity of pre-existing cartilage damage may also contribute to the risk of conversion to TKA.