Validation of navigation assisted cup placement in total hip arthroplasty

Computer navigation has the potential to provide precise intraoperative knowledge to the surgeon. Previous studies with navigation have confirmed its function for improved component position but few studies have reported the accuracy and precision of navigation system in clinical use. With this study we propose to evaluate the efficacy of navigation in guiding cup placement.

Fifty-six patients undergoing primary total hip arthroplasty were prospectively included in this study. Stryker imageless navigation system which is accurate to 0.5° was used in all cases. Intraoperative data was collected for the acetabular component position using navigation for the freehand cup placement and the final cup placement done using navigation. Postoperative evaluation of component position was done with computed tomography (CT) and the deviation from intraoperative freehand and navigation values were calculated.

The mean inclination of the freehand reading was 39.5° (range, 20°-58°), mean version of freehand reading was 10.7° (-6°- 27°), and the mean navigation reading was 43.2° (37°-49°) for inclination and 13.0° (-8° - 24°) for version. On postoperative CT scan analysis the mean inclination was 45.3° (34°-56°) and mean version was 15.1° (4°-25°). The deviation of the freehand inclination from the post operative CT scan reading was 11.4° (1°-30°) and the version deviated by a mean of 10.8° (2°-26°). The deviation of the navigation reading from the CT scan reading had a mean of 5.3° (1°-13°) for inclination and 5.6° (1°-17°) for version.

The accuracy of the navigation system over conventional freehand cup placement is validated by this study.