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

Abstract Background 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. 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 alignment guide in the supine or lateral positions. Methods This retrospective study included 136 consecutive patients (105 women, 31 men; mean age, 66.4 years) who underwent primary cementless THA via an anterolateral approach. The accuracy of cup orientation was compared among the three registration methods using postoperative CT. Results The absolute value of the difference in cup inclination with the NAVBIT (2.6° ± 2.2°) was comparable to that with the cup alignment guide in the supine position (3.5° ± 2.5°) and smaller than that with the cup alignment guide in the lateral decubitus position (3.9° ± 2.7°). The absolute values of the difference in cup anteversion with the NAVBIT (2.2° ± 1.6°) were smaller than that with the cup alignment guide in the supine (3.7° ± 1.9°) and lateral decubitus positions (4.5° ± 3.4°). Eighty-one percent, 63.4%, and 48.8% were within 5° of the target angles in the navigation, supine alignment guide, and lateral alignment guide groups, respectively. Conclusions The accuracy of cup alignment with the portable navigation system using the flip technique was significantly higher than that with the cup alignment guide in the supine and lateral decubitus positions.