 The purpose of this study is to monitor the performance and determine the metal ion release of the DePuy ASRTM System in the treatment of patients with hip joint disease requiring hip resurfacing surgery. Patients who enter the study will be evaluated at regular intervals following hip surgery using patient, clinical and x-ray assessments. A subset of patients will also have blood samples taken at regular intervals to allow the metal ion levels to be determined and undergo scans to allow the bone mineral density of the bone surrounding the implant to be monitored. 