MRI based computer navigation of total hip replacement

INTERVENTION: Navigation of hip joint replacement based on MRI preop findings. Follow up results with CT scan A standard MRI scan of the hip was used preoperatively to investigate the patient's hip anatomy in order to design the navigation tool specific to each patient. This takes approximately 30 minutes over one day. One scan is required before the operation for each patient. A CT scan of the pelvis is obtained post‐operatively to assess the position of the acetabular component and this is to be compared between the MRI navigation group and the standard free hand group. This takes approximately 30 minutes over one day. One scan is required for each patient. CONDITION: Osteoarthritis of hip joints PRIMARY OUTCOME: Position of acetabular cup based on CT scan of the pelvis post op SECONDARY OUTCOME: Complications of MRI based navigation technique ; The MRI navigation tool is a pilot study. The main different feature of this navigation is the use of MRI scan prior to surgery. MRI scan is a safe procedure without any harm to the patients. ; During surgery the navigation will use a cutting block to fit into the specific patient's pelvis and the block secured wires into the pelvis. This has been safely applied oversea without any complications clinically. However potential complications such as fracture and infection associated with this can be assessed with CT scan following surgery and subsequent follow up of patient's progress at outpatient clinic. Appropriate blood tests will be obtained if there is a clinical suspicion of infection. INCLUSION CRITERIA: Osteoarthritis of hip joint