Learning Curve of Robot-Assisted Total Hip Arthroplasty: Cumulative Sum Analysis

Robot-assisted total hip arthroplasty (RA-THA) has been developed to enhance implant placement accuracy and minimize surgical variability. Although potential benefits have been demonstrated, adoption is accompanied by a learning curve. This study aimed to evaluate the learning curve associated with RA-THA using a single robotic platform.

In this prospective design and retrospective review study, 40 consecutive RA-THA procedures were performed between March and April 2025, marking the initiation of a robotic hip program. All procedures utilized the MAKO robotic system (Stryker). Step-specific operative times, including pelvic array fixation, dissection and bone preparation, landmark registration, and acetabular reaming and impaction, were prospectively recorded by an independent observer. The learning curve was analyzed using cumulative sum (CUSUM) analysis.

CUSUM analysis identified 2 distinct phases: a learning phase (first 11 cases) followed by a proficiency phase. Significant reductions in operative times were observed for robotic-specific steps, particularly pelvic array fixation and landmark registration, during the proficiency phase (p < 0.05). There was no significant difference between the 2 phases in terms of acetabular cup positioning. The mean inclination angle was 38.9° ± 1.5° (range, 37-41), with all cases within the Lewinnek safe zone. Anteversion remained within 3° of the planned target, and combined anteversion was maintained within the safe range of 25°-50°.

The learning curve for RA-THA using the MAKO system reached a plateau after 11 cases, with improved efficiency in robotic-specific steps. Accurate and reproducible cup positioning was maintained throughout the series, suggesting that the technical benefits of robotic assistance are realized early in the learning process.