Outcome predictors of intertrochanteric osteotomy in avascular necrosis of the hip]

PURPOSE OF THE STUDY: To find radiographic predictors for the clinical outcome in patients who underwent an intertrochanteric osteotomy (ITO) because of avascular necrosis of the femoral head (AVN). METHOD: Between 1985 and 1996 in 93 patients with an AVN (mean age 39,5 years +/- 8.8 y.) an ITO was performed. 83 patients (89 %) were available for follow up at an average post-op time of 84 months +/- 40.7 mon. We used the Ficat and ARCO classifications for staging of the disease. The combined necrotic angle of Kerboul was used to measure the size of the lesion. The clinical outcome was estimated using the Harrisp hip score (HHS) and the WOMAC. Survival time of the ITO was estimated using Kaplan-Meier survivorship analysis with the implantation of a hip prosthesis as endpoint. RESULTS: 27 patients (30.8 %) underwent an arthroplasty after an average time of 35.1 mon. +/- 30,4 mon. after the osteotomy. Survival rate of an ITO was 67 % after 5 y, and 46 % after 10 y. In case of a preoperative Kerboul angle > 200 degrees the survival rate of an ITO was significantly lower and the WOMAC index (3.1 +/- 2.4) significantly worse (p < 0.05) than in patients with a Kerboul angle < 200 degrees (1,8 +/- 1.8). In Ficat stage III/IV or ARCO stage IVVI the survival rate of an ITO was significantly lower when compared to stages I/II and IIII. There was no clinical difference in the HHS comparing different stages. CONCLUSION: The Kerboul angle was the best parameter to predict the clinical outcome and the survival rate of an ITO. The classifications of Ficat and ARCO were found to be a predictor for the survival rate of an ITO but not for the clinical outcome.