Comparison of cup placement angles accuracy of total hip arthroplasty using the Augmented Reality hip navigation system in supine and lateral positions

Introduction: We aimed to compare the accuracy of acetabular cup positioning angles between supine and lateral total hip arthroplasty (THA) using an augmented reality hip navigation system (AR Hip) and identify predictive risk factors for cup placement angles in lateral THA. Materials and Methods This study included 139 THA procedures performed using the AR Hip between June 2021 and July 2024 (mean age 66.1 years, 25 males, 114 females). To match the patient backgrounds between the groups, propensity score matching (PSM) was performed using sex, age, height, weight, and Crowe classification as covariates. The absolute error in the difference between the intraoperative navigation records and postoperative measurements using computed tomography data was evaluated between the supine and lateral positions. Additionally, we conducted a multivariate analysis to identify preoperative clinical factors associated with positioning errors ≥ 5° in the lateral position. Results In the supine group after PSM, the average absolute errors were 2.9° for both inclination and anteversion. In the lateral position group, the mean absolute errors were 2.2° and 1.9 °for inclination and anteversion, respectively. No significant difference was observed between the two groups in terms of average absolute error. Additionally, multiple regression analysis revealed that pelvic tilt (odds ratio 0.8; 95% confidence interval 0.69–0.98; p  = 0.03) was a predictive factor for inaccuracy of cup placement angle. Conclusions When using the AR Hip, no significant cup positioning accuracy difference was noted between supine and lateral THA. In cases of severe preoperative pelvic posterior tilt, cup positioning accuracy may be adversely affected.