Femoral neck fractures after metal-on-metal total hip resurfacing: a prospective cohort study.

There has been a renewed interest in metal-on-metal resurfacing total hip arthroplasty. Recent studies have reported high success rates at short to midterm follow-up. Despite these excellent early outcomes, femoral neck fractures have been reported as a major complication after this procedure. The purpose of this study was to identify the incidence of this complication in a prospective cohort of patients. In addition, various demographic and radiographic factors such as surgeon experience, age, sex, body mass index, femoral neck notching, and cysts were assessed as potential risk factors. Between November 2000 and August 2006, 550 metal-on-metal total hip resurfacings were performed by a single surgeon. The absolute risk for femoral neck fracture in this cohort was 2.5%. Of the 14 fractures, 12 occurred in the first 69 resurfacings performed. After this time, the incidence of fracture was 0.4%. Women and obese patients were shown to have higher cumulative incidences of fractures. These findings suggest the need for careful patient selection and surgical technique, especially for surgeons during the early learning curve for this technically difficult surgery.