Sex-specific risk factors determine the survivorship of female and male patients after metal-on-metal hip resurfacing

Background: The need for revision surgery after hip resurfacing arthroplasty (HRA) is more prevalent for women than for men. However, there is a paucity of information to explain this observation. We aimed (1) to determine sex-specific risk factors leading to revision surgery; and (2) to correlate these risk factors to the dominant modes of failure of HRA. Methods: 1101 patients (1375 consecutive hips) including 292 women (355 hips) and 809 men (1020 hips) with a mean age of 51.3 years were included regardless of bone quality. The contact patch to rim distance was computed. Results: A contact patch to rim (CPR) distance of <= 7 mm, an aetiology of developmental dysplasia, a postoperative abduction-adduction arc of > 95 degrees, and a metaphyseal stem left uncemented were risk factors associated with revision surgery for female patients, while a CPR distance of <= 10 mm, a component size of <= 46 mm, an age at surgery of <= 55 years, and an early femoral preparation technique were risk factors for male patients. Hips with no risk factors from the female group had a survivorship of 98.7% at 15 years, matching or exceeding the results of all male subgroups. However the risk factors in the female group increased the risk of revision much more than in the male group. Conclusions: In the absence of risk factors, the survivorship of HRA in female patients is equal to that of males. Many female patients can safely benefit from HRA by excluding severe dysplasia and optimising surgical technique.