 The purpose of this study is to monitor the performance and compare the metal ion release of two bearing combinations, ceramic-on-metal and metal-on-metal in the treatment of patients with hip joint disease requiring a total hip replacement. Patients who enter the study will be randomly allocated to one of the bearing combinations and will be evaluated at regular intervals using, patient, clinical and x-ray assessments. Patients will also have blood samples taken at regular intervals to allow the metal ion levels to be determined. 