Augmented reality-based portable navigation improves accuracy of cup placement in total hip arthroplasty with a short learning curve

Malpositioning of the acetabular cup in total hip arthroplasty (THA) can cause complications including dislocation, wear, and aseptic loosening. Although computed tomography (CT)-based navigation systems have improved THA accuracy, the high cost and complexity of these systems have hindered their widespread use. Therefore, this study investigated the accuracy and learning curve of an augmented reality (AR)-based portable navigation system. This retrospective study analyzed 106 hips in 87 patients who underwent primary THA using an AR-based portable navigation system between July 2023 and December 2024. A single surgeon performed all surgeries. The accuracy of the intraoperative navigation records for cup inclination and anteversion was assessed by comparing them with postoperative CT-based measurements. Absolute error values exceeding 5° and 10° were defined as outliers > 5° and > 10°, respectively. Receiver operating characteristic (ROC) analysis was used to evaluate the learning curve, and multivariate logistic regression identified risk factors associated with cases classified as outliers (> 5°). The mean absolute errors between the navigation records and postoperative measurements were 2.2° for inclination and 3.8° for anteversion. Outliers > 5° were observed in 31% of cases, while outliers > 10° were rare (2.8%). No dislocations or revisions occurred within six months. Learning curve analysis showed consistent accuracy in the initial cases. The only significant predictor of navigation error was intraoperative posterior pelvic tilt change (odds ratio 1.13, p = 0.04). Body mass index and subcutaneous fat thickness were not significantly different. The AR-based portable navigation provided highly accurate acetabular cup placement without a learning curve. However, excessive intraoperative posterior pelvic tilt increased the risk of anteversion overestimation, highlighting the need for intraoperative pelvic position management.