<qa>  What is the purpose of the study?The purpose of this study is to monitor the performance and determine the metal ion release of the PinnacleTM Cup with a metal-on-metal bearing combination in the treatment of patients with hip joint disease requiring a total hip replacement. 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. 