Accuracy of cup alignment in total hip arthroplasty – a comparison between the portable navigation and goniometer

Navigation systems, including portable navigation systems, used for total hip arthroplasty (THA) are useful for achieving higher cup alignment accuracy. NAVBIT, a newly available portable navigation system, uses a unique registration method, the table tilt registration. However, its accuracy is unclear. This retrospective study aimed to investigate whether THA with a portable navigation system in the lateral position with the flip technique is more accurate than THA with a cup goniometer in the supine or lateral positions. This study included 96 consecutive patients (77 women, 19 men). The accuracy of cup orientation was compared among the three groups. The absolute values of the difference in cup inclination and anteversion with the NAVBIT (2.1 ± 1.7°, 2.0 ± 1.4°) were smaller than that with the cup goniometer in the supine (3.4 ± 2.4°, 3.4 ± 2.2°) and lateral decubitus positions (3.4 ± 2.5°, 5.0 ± 3.5°). Ninety-one percent, 64.5%, and 56.3% were within 5° of the target angle in the navigation, supine goniometer, and lateral goniometer groups, respectively. The accuracy of cup alignment with the portable navigation system using the flip technique was significantly higher than that with the cup goniometer in the supine and lateral decubitus positions.