Motion analysis after total hip arthroplasty using a combined acetabular and femoral navigation system

A Combined acetabular and femoral navigation system (CAF system) for total hip arthroplasty (THA) was developed to perform accurate placement of the acetabular and femoral components, as well as to evaluate the range of hip motion through motion analysis. Twenty-four patients underwent THA for osteoarthritis secondary to hip dysplasia under the CAF system, and the position of the cup and the stem, range of motion, and the motion center of the hip joint were evaluated. Accurate cup and stem placement according to the preoperative computer simulation was confirmed in most cases. Through the motion analysis, concomitant pelvic movement accompanying the joint movement was noted. The CAF navigation system was useful to evaluate relative range of motion by taking account of the concomitant pelvic movement, to detect impingement of the stem against the surrounding bony structure or the cup edge, and to offer guidance of individual postoperative education of the safe movement to prevent postoperative dislocation.