Long‐term outcomes of transtrochanteric rotational osteotomy for non‐traumatic osteonecrosis of the femoral head

Aims Transtrochanteric rotational osteotomy (TRO) is performed for young patients with nontraumatic osteonecrosis of the femoral head (ONFH) to preserve the hip. We aimed to investigate the long‐term outcomes and the risk factors for failure 15 years after this procedure. Patients and Methods This study included 95 patients (111 hips) with a mean age of 40 years (21 to 64) who underwent TRO for ONFH. The mean follow‐up was 18.2 years (3 to 26). Kaplan‐Meier survivorship analyses were performed with conversion to total hip arthroplasty (THA) and radiological failure due to secondary collapse of the femoral head or osteoarthritic changes as the endpoint. Multivariate analyses were performed to assess risk factors for each outcome. Results Survival rates at 15 years with conversion to THA and radiological failure as the endpoint were 59% (95% confidence interval (CI) 49 to 67) and 30% (95% CI 22 to 39), respectively. Necrotic type C2 ONFH (lesions extending laterally to the acetabular edge) (hazards ratio (HR) 3.9) and age > 40 years (HR 2.5) were risk factors for conversion to THA. Stage > 3a ONFH (HR 2.0) and age > 40 years (HR 1.9) were risk factors for radiological failure. Conclusion The 15 year outcomes after TRO for ONFH are unfavorable because osteoarthritic changes occur after five years post‐operatively.