Older age and female gender are independent predictors of early conversion to total knee arthroplasty after high tibial osteotomy.

BACKGROUND

The primary aim was to assess survival of opening wedge high tibial osteotomy (HTO) for medial compartment osteoarthritis. The secondary aim was to identify independent predictors of early conversion to total knee arthroplasty (TKA).

METHODS

During the 18-year period (1994-2011) 111 opening wedge HTO were performed at the study centre. Mean age was 45 years (range 18-68) and the majority male (84%). Mean follow-up was 12 (range six to 21) years. Failure was defined as conversion to TKA. Kaplan-Meier, Cox regression and receiver operating curve (ROC) analyses were performed.

RESULTS

Forty (36.0%) HTO failed at a mean of 6.3 years (range one to 15). By Kaplan-Meier analysis, the five-year survival rate was 84% (95% confidence interval (CI) 82.6-85.4), 10-year rate 65% (95% CI 63.5-66.5) and 15-year rate 55% (95% CI 53.3-56.7). Cox regression analysis identified older age (hazard ratio (HR) 1.07 for each additional year, 95% CI 1.03-1.11, p b 0.001) and female gender (HR 2.37, 95% CI 1.06-5.33, p = 0.04) as independent predictors of failure. ROC analysis identified a threshold age of 47 years above which the risk of failure increased significantly (area under curve 0.72, 95% CI 0.62-0.81, p b 0.001). Cox regression analysis, adjusting for covariates, identified a significantly greater (HR 2.49, 95% CI 1.26-4.91, p = 0.01) risk of failure in patients aged 47 years old or more.

CONCLUSION

The risk of early conversion to TKA is significantly increased in females and those older than 47. These risk factors should be considered pre-operatively when planning intervention for isolated medial compartment osteoarthritis.