ObjectiveTo evaluate the clinical and radiographic outcomes of hip resurfacing arthroplasty (HRA) for treating osteonecrosis of the femoral head (ONFH) in young and middle-aged patients. MethodsBetween January 2008 and April 2009, 34 patients with ONFH underwent HRA. There were 19 males and 15 females with an average age of 54 years (range, 33-59 years). Of 34 cases, 16 left hips and 18 right hips were involved, including 9 cases of alcoholinduced ONFH, 8 cases of steroid-induced ONFH, 7 cases of traumatic ONFH, and 10 cases of unexplained ONFH. According to modified Ficat classification system, 26 hips were rated as stage III, and 8 hips as stage IV. The Harris hip score (HHS) and modified University of California, Los Angeles (UCLA) activity score were used to evaluate the clinical results. Migration of prosthesis was assessed on the anteroposterior radiographs. The abduction angle was measured on the acetabular side. On the femoral side, varus-valgus shift was determined by measurement of stem-shaft angle. The axial collapse of femoral component was assessed with the component-lateral cortex ratio. ResultsHealing of incision by first intention was achieved in all patients without complications of infection and thrombosis of deep vein of lower extremities. Thirty-two patients were followed up 78 months on average (range, 70-84 months). No implant loosening, infection, femoral neck fracture, dislocation, and inflammatory pseudotumor were observed. At last follow-up, the HHS score was significantly increased to 95.22±1.47 from preoperative 50.10±2.27 (t=1.510, P=0.008). Modified UCLA activity score was significantly increased to 7.70±1.13 from preoperative 3.90±0.90 (t=0.830, P=0.003). The abduction angle, stemshaft angle, and compotent-lateral cortex ratio showed no significant difference between at 3 days after operation and last follow-up (P>0.05). ConclusionIf the indication of operation is mastered strictly, HRA may be effective in treatment for ONFH at Ficat stage III or IV in young and middle-aged patients.