A Study to Demonstrate the Accuracy of Femoral Neck Resection Compared to the Pre-operatively Selected OPS™ Plan in Total Hip Arthroplasty.

Total Hip Replacement (THR) is the gold standard for treatment of severe arthritis of the hip as it relieves pain, restores function of the joint and improves quality of life for patients. The restoration of hip mechanics can be influenced by the selected femoral stem design and also by choices made by the surgeon during the surgical implantation. The combination of femoral neck resection level and angle are key factors, particularly in cementless hip arthroplasty, in determining post-operative leg length and femoral anteversion. Historically, an estimation of prosthesis sizing and positioning has been made via a process of manual or digital templating either pre or intraoperatively using images of the implants positioned over the standard AP and lateral view hip x-rays taken in advance of surgery with generic instruments used during the surgery to execute the femoral head resection at the planned level. This process has a number of limitations. The OPS™ system utilizes detailed pre-operative imaging including a CT scan to generate a plan for the femoral neck resection level and angulation based on the anatomy of the individual patient. Following validation of this plan by the operating clinician, a patient specific femoral guide instrument is generated to help facilitate the reliable delivery of the planned resection intraoperatively. The purpose of this study will be to evaluate the use of the patient-specific femoral instrument in the hands of two surgeons using different prosthesis combinations and surgical approaches. A total number of 40 participants will be enrolled. Participants in this study will return for a single post-operative visit at 6 weeks to have X-rays taken and to enable any post-operative study hip related complications to be recorded. Once this has been completed, participants will be routinely followed-up by their orthopaedic surgeon as required in accordance with standard clinical practice.