CT image evaluation of the internal rotation limit prior to bony impingement after total hip arthroplasty.

This study evaluated the internal rotation limit prior to bony impingement of the proximal femur on the pelvis after total hip arthroplasty (THA). Reconstructed computed tomography (CT) images of 90 degrees hip flexion were used to simulate the internal rotation limit against safety limits measured intraoperatively. Ninety joints in 86 subjects (12 men and 74 women) underwent THA for the treatment of secondary coxarthrosis. The correlation between the internal rotation limit prior to the bony impingement intraoperatively and the simulated internal rotation angle on the reconstructed CT image was statistically significant. We provide a new method to simulate the internal rotation limit prior to bony impingement based on postoperative CT.