Total knee arthroplasty after high tibial osteotomy: analysis of time to event and predictors

Context: An important goal of high tibial osteotomy (HTO) is to prevent or delay the need for total knee arthroplasty (TKA). We aimed to estimate the frequency and timing of conversion from HTO to TKA and identify associated factors. Methods: We prospectively evaluated patients with knee osteoarthritis, or gonarthrosis, who underwent medial opening valgization HTO between 2002 and 2014 and analyzed the cumulative incidence of TKA as of July 2019. The presence or absence of a TKA involving the limb undergoing HTO was determined from orthopedic surgery notes and knee radiograph reports in each patient's electronic medical record at London Health Sciences Centre. We used cumulative incidence curves to assess the primary end point, time to HTO. We performed a multivariate Cox proportional hazards analysis to assess potential preoperative predictors, including radiographic disease severity, misalignment, extent of correction, pain, sex, age, body mass index (BMI), and year of surgery. Results: Of 556 patients with 643 HTOs, the cumulative incidence of TKA was 5% (95% confidence interval [CI] 3%-7%) at 5 years and 21% (95% CI 17%-26%) at 10 years. With the multivariate Cox proportional hazards model, the following preoperative factors were significantly associated with increased conversion rates: OA severity on radiography (adjusted relative risk [RR] 1.96; 95% CI 1.12-3.45), pain (adjusted RR 0.85; 95% CI 0.75-0.96), female gender (adjusted RR 1.67; 95% CI 1.08-2.58), age (adjusted RR 1.50 per 10 years; 95% CI 1.17-1.93), and BMI (adjusted RR 1.31 per 5 kg/m2; 95% CI 1.12-1.53).Interpretation: We found that 79% of knees did not require TKA within 10 years of medial opening valgus Interpretation: We found that 79% of knees did not require TKA within 10 years of medial opening valgus HTO. The strongest predictor of conversion to TKA was the severity of disease on radiography performed at the time of HTO. The strongest predictor of conversion to TKA was the severity of disease on radiography performed at the time of HTO.