Is a new type of socket joint of a hip prosthesis stable without the use of screws in patients undergoing total hip replacement?

INTERVENTION: Primary total hip replacement using a tantalum trabecular metal coated acetabular shell. This is a surgical procedure where the femoral head is removed and replaced by a 28 mm metal prosthetic femoral head, which is attached to a femoral stem inserted into the femur. The head then articulates with a plastic (highly cross‐linked polyethylene) liner in a metal acetabular shell, which is inserted into the acetabulum. Initial stability of the shell is achieved by press‐fit fixation, without the use of screws. The duration of the operation is between about 45 minutes and 4 hours, depending on the complexity of the operation. During the operation tiny tantalum beads are inserted into the periprosthetic bone to enable determination of acetabular component migration using a highly sophisticated radiographic technique, namely radiostereometric analysis. CONDITION: Migration of the acetabular component of a total hip replacement prosthesis PRIMARY OUTCOME: Percentage of patients with acetabular shell migration exceeding 1 mm, as measured by radiostereometric analysis. SECONDARY OUTCOME: Mean acetabular component migration, as measured by radiostereometric analysis INCLUSION CRITERIA: 1. undergoing primary total hip replacement through posterior approach 2. diagnosis of osteoarthritis 3. walking ability restricted only by hip pathology