Evaluation of the Accuracy of Intraoperative Femoral Stem Anteversion Using a Mechanical Alignment Guide and a CT-Based Navigation System

Background In total hip arthroplasty (THA), implant position is one of the critical factors affecting implant longevity, clinical outcomes, and postoperative complications. Although a number of studies have reported the accuracy of acetabular component positioning using a computed tomography (CT)-based navigation system, the significance of femoral stem anteversion has not been well addressed in the literature. Methods Stem anteversion in 83 patients who underwent primary THA and bipolar hemiarthroplasty was simultaneously measured with both a CT-based navigation system and a mechanical alignment guide during surgery. Both intraoperative measurement values were compared with the postoperative measurement values using the same three-dimensional coordinate system. Results The absolute discrepancy between the mechanical alignment guide value and the postoperative stem anteversion was 7.6° ± 5.2° (range: 0° to 17°). On the other hand, the absolute discrepancy between the intraoperative stem anteversion value measured with CT-based navigation and the postoperative stem anteversion was 2.9° ± 3.1° (range: 0° to 14°). The absolute discrepancy was significantly lower in intraoperative CT-based navigation (p = 0.001). Conclusion Intraoperative stem anteversion measurements using CT-based navigation were more accurate than those using the mechanical alignment guide.