Accuracy of Computer Navigation for Acetabular Component Placement in THA

The accuracy and precision of any computer-aided surgical device is critical to its utility. We asked the following question: how accurate and precise are the values measured by an imageless computer navigation system as compared with those measured using postoperative CT scans? Twenty-five patients (26 hips) underwent primary THA using an imageless computer navigation system for placement of the acetabular component. Inclination and anteversion were measured in the operative coordinate system as defined by Murray. Accuracy, precision, and bias were computed, and Bland-Altman analysis was used to assess levels of agreement. The accuracy (mean ± standard deviation of the absolute difference between computer-assisted navigation and CT) was 1.8° ± 1.2° for inclination and 2.0° ± 2.0° for anteversion. Precision was 3.4° for inclination and 5.5° for anteversion. Bias was 0.52° for inclination and 0.35° for anteversion. Limits of agreement were 4.26° for inclination and 5.58° for anteversion. An imageless computer navigation system can precisely determine acetabular cup position.