Accuracy of acetabular cup installation angles using two augmented reality navigation systems: computed tomography-based and noninvasive portable systems in total hip arthroplasty

This study compared the accuracy of acetabular cup installation angles in total hip arthroplasty (THA) between a CT-based augmented reality (AR) navigation system and a noninvasive AR portable navigation system used simultaneously during surgery. Both navigation systems can be used with acetabular components from multiple manufacturers. This study included 48 hips across 44 patients who underwent primary cementless THA in the supine position. Acetabular cup placement was guided by the AR CT-based navigation system, whereas the noninvasive AR portable navigation system provided a single static measurement after cup fixation. The cohort consisted of 12 male and 36 female hips, with a mean age of 69 years and a mean body mass index (BMI) of 24 kg/m². The target angles for cup placement were 40° for radiographic inclination (RI) and 15° for radiographic anteversion (RA). Navigation errors were defined as the absolute difference between intraoperative navigation values and postoperative CT measurements and compared between groups. RI navigation errors were similar (CT-based AR group vs. noninvasive AR portable group: 2.4°±2.0° vs. 2.8°±2.4°; not significant). In contrast, RA navigation errors were significantly smaller in the CT-based AR group (2.3°±1.8°) than in the noninvasive AR portable group (3.2°±2.4°; p < 0.05). No significant factors influencing navigation errors were identified in either group. In supine THA, under these static measurement conditions, RI navigation error did not differ significantly between the two systems, whereas RA navigation error was significantly greater with the noninvasive AR portable navigation system than with the AR CT-based navigation system.