Purpose of the study: To find predictors for the clinical outcome in patients who underwent a high tibial osteotomy [HTO].

Method: Between 1984 and 1996 in 155 patients with genu varum a high tibial valgus osteotomy was performed. 133 HTOs were available for follow up at an average post-op time of 9.3 years (3,0 y). The morphology of the knee was evaluated by radiological (Kellgren) and arthroscopical classifications (Outerbridge). Survival time of HTO was estimated using Kaplan-Meier survivorship analysis. Patients outcome was evaluated using the WOMAC score. For statistical analysis Log-rank test and Wilcoxon-Mann Whitney U-Test were used.

Results: During follow up time 19.8% of patients needed a total knee arthroplasty. Survival rate of HTO was 95% after 5 years and 77% after 10 years. In the medial compartment of knee joints with a preoperative Outerbridge stage III/IV or Kellgren stage III/IV the survival rate of HTO was significantly lower when compared to stages I/II (p< 0,05).

Age, sex, dimension of the mechanical medial proximal tibial angle (mMPTA) and severity of arthrosis in the lateral compartment had no influence on survival rates. The pre-postoperative comparison of radiologically visible signs of arthrosis showed either no or only small progress. The patients who underwent a HTO had an average of 1,9 points on the WOMAC score (global index 0–10) which is a good to very good clinical outcome.

Conclusion: We identified the severity of the preoperative radiological signs of arthrosis and the extent of chondromalacia noted intraoperatively as predictors of survival rate.