Accuracy of cup orientation and learning curve of the accelerometer-based portable navigation system for total hip arthroplasty in the supine position

Purpose: To assess the accuracy of cup orientation and learning curve of the disposable accelerometer-based portable navigation system for total hip arthroplasty (THA) in the supine position. Methods: A total of 75 patients who underwent THA through the anterolateral supine approach (ALS) with an accelerometer-based portable navigation system for the supine position (HipAlignA (R)) between July 2017 and October 2018 were analyzed in this study. We compared the intraoperative cup angles using navigation records with the postoperative angles using postoperative computed tomography (CT) data. All patients were categorized into the following groups according to the course of three discrete, sequential operative time periods: 1-25 (initial group), 26-50 (intermediate group), and 51-75 (recent group). We compared the accuracy of cup inclination and anteversion among the three groups. The time required for navigation and the operative time of all patients were measured. Results: The average absolute error in measurement (postoperative CT-navigation record) was 2.6 degrees +/- 2.7 degrees (inclination) and 2.8 degrees +/- 2.7 degrees (anteversion). There were no significant differences among the three groups. The average time required for navigation and the operative time were 365.1 +/- 90.3 s and 76.1 +/- 1.6 min, respectively. The required time for HipAlignA (R) navigation and operative time were constant in most patients, except for those of the initial five cases. Conclusion: The accelerometer-based portable navigation system provides good accuracy of cup orientation, has a short learning curve, and requires a minimal surgical time for THA in supine position.