[Original Article]Long-term results of femoral curved varus osteotomy for idiopathic osteonecrosis of the femoral head

[ABSTRACT]【Objective】The purpose of this study was to document the long-term results of femoral curved varus osteotomy (CVO) for osteonecrosis of the femoral head (ONFH) and to identify a predictive factor for the outcome.【Methods】From April 1997 through April 2018, 32 patients (39 hips) underwent CVOs for idiopathic ONFH. Mean age at surgery was 33.0 years (standard deviation [SD] 8.9). Potential causative factors of ONFH were corticosteroid in 30 hips, alcohol in five hips, and “idiopathic” causes in four hips. 【Results】Survival rates after CVO were 96% at 5 and 10 years and 84% at 15 years with total hip arthroplasty (THA) as the endpoint. Survival rates after CVO were 68% at 5 years, 46% at 10 years, and 28% at 15 years with osteoarthritic change as the endpoint. The Japanese Orthopaedic Association hip score significantly improved from 67.5 (SD 19.1) points before surgery to 86.5 (13.6) points one year after CVO and 93.0 (20.7) points at the final follow-up (p = 0.0002). 【Conclusion】The long-term results of CVO for ONFH were favorable with ten-year survival rates of 96% using conversion to THA as the endpoint. The postoperative intact ratio was suggested to be a predictive factor for OA change after CVO.