Effect of improved navigation performance on the accuracy of implant placement in total hip arthroplasty with a CT-based navigation system

A computed tomography (CT)-based navigation system is one of the support tools to place implant with appropriate alignment and position in total hip arthroplasty (THA). To determine whether the higher performance of the navigation would further improve the accuracy of implant placement in the clinical setting, we retrospectively compared the navigation accuracy of two different versions of a navigation system. The newer version of the navigation system had an upgraded optical sensor with superior positional accuracy. Navigation accuracy, defined as differences between postoperative measurements on CT images and intraoperative records on the navigation system, of 49 THAs performed with the newer version of the navigation system was compared with that of 49 THAs performed with the older version. With the newer version, the mean absolute accuracy (95% limits of agreement) of implant alignment was 1.2 degrees (+/- 3.3 degrees) for cup inclination, 1.0 degrees (+/- 2.4 degrees) for cup anteversion, 2.0 degrees (+/- 4.9 degrees) for stem anteversion, and 1.1 degrees (+/- 2.4 degrees) for stem valgus angle. The accuracy of the implant position was 1.5 mm (+/- 3.1 mm), 1.3 mm (+/- 3.0 mm), and 1.5 mm (+/- 3.1 mm) for cup x-, y-, and z-axes, respectively, 1.6 mm (+/- 3.2 mm), 1.4 mm (+/- 2.9 mm), and 1.5 mm (+/- 2.7 mm) for stem x-, y-, and z-axes, respectively, and 2.4 mm (+/- 4.5 mm) for leg length discrepancy. The values for the newer version were significantly more accurate with less variation compared to those of the older version. With upgraded navigation performance, more accurate implant placement was demonstrated in the clinical setting.