Evaluation of the Accuracy of Computed Tomography-Based Navigation for Femoral Stem Orientation and Leg Length Discrepancy

Although there is a great deal in the literature about the clinical accuracy of computed tomography (CT) based navigation systems for acetabular cup orientation and leg length discrepancy in total hip arthroplasty, there is little analysis of femoral stem orientation. Thirty total hip arthroplasties in which CT-based navigation system had been used had their anteversion, valgus angle of stem, and leg length discrepancy measured on postoperative CT data. Differences in postoperative measurements from intraoperative records were -0.6 degrees +/- 4.8 degrees (range, -11 degrees to 10 degrees) for stem anteversion, -0.2 degrees +/- 1.8 degrees (range, -4 degrees to 3 degrees) for valgus angle of stem, and 1.3 +/- 4.1 mm (range, -6 to 10 mm) for leg length. Although this system may need further improvement for stem orientation, it was helpful for intraoperative leg length adjustment.