Factors related to disagreement in implant size between preoperative CT-based planning and the actual implants used intraoperatively for total hip arthroplasty

Purpose In total hip arthroplasty, prediction of the optimal implant size is important in order to prevent perioperative complications. However, it is not easy to achieve complete agreement between the planned size and the actual size required appropriate implant fit. No previous report has adequately discussed the factors related to mismatch between predicted and actual implant sizes. The purpose was to report the results of a single surgeon case series of patients undergoing THA using computed tomography (CT)-based templating and the possible factors related to implant size mismatch. Methods The study included 141 hips of 126 patients who underwent primary total hip arthroplasty with CT-based navigation. We retrospectively reviewed the planned and actual implant sizes used in these patients. Cup position, cup orientation and stem alignment were evaluated as surgical factors that could possibly be related to mismatch in implant size. Cortical index and canal flare index were also evaluated as morphological factors. Results The final inclusions in this study were 124 hips of 111 patients including 82