Duration of symptoms and outcome of hemiresurfacing for hip osteonecrosis.

Thirty-seven hips with Ficat Stage II, III, or early IV osteonecrosis were treated with hemiresurfacing. The purpose of this study is to analyze specifically the clinical and radiographic results of patients who had hemiresurfacing to refine the indications for the procedure and identify factors substantially affecting clinical outcome and survivorship. At an average followup of 6.5 years, the average University of California Los Angeles hip scores for pain, walking, function, and activity improved significantly from 4.3, 6.0, 5.3, and 4.2 to 8.0, 8.8, 7.9, and 5.8. The overall survivorship was 79%, 59%, and 45% at 5, 10, and 15 years. Eleven hips have been converted: 10 hips for acetabular cartilage wear and one hip for femoral loosening. The average time to conversion was 7.5 years. A longer duration of symptoms before surgery (16.6 months versus 12.1 months) was associated with a worse acetabular cartilage grading and suggested a relationship with a shorter time to conversion, although the difference was not statistically significant at the 5% level. Survivorship is better when preoperative symptoms are present for 1 year or less, possibly because the articular cartilage is healthier. When necessary, conversion to total hip replacement can be done without adverse results.