Robot-assisted elimination of side disparity in acetabular cup placement by right-handed surgeons during total hip arthroplasty: a comparative study of manual and robotic techniques

Total hip arthroplasty (THA) requires precise acetabular cup placement to ensure long-term success. Despite the widely accepted “safe zone,” manual THA outcomes can be influenced by surgeon handedness, leading to side-dependent disparities in cup positioning, especially among right-handed surgeons. This study aimed to compare the consistency of acetabular cup placement between left and right sides in robotic-assisted (RA-THA) versus manual THA (M-THA) performed by right-handed surgeons. A retrospective cohort of 220 patients who underwent primary unilateral THA via posterolateral approach was included. Patients were divided into RA-THA (n = 110) and M-THA (n = 110) groups, each further stratified by operative side (left/right). Radiographic parameters (inclination, anteversion, limb length discrepancy, femoral/acetabular offset), safe zone achievement, perioperative outcomes, and early clinical results were assessed. Results showed that in the M-THA group, left-side procedures exhibited significantly greater anteversion (25.5°±6.2° vs. 22.9°±3.8°, p = 0.009), larger limb length discrepancy (0.7 ± 0.3 mm vs. 0.5 ± 0.2 mm, p < 0.001), and greater offset deviations compared to right-side procedures. In contrast, the RA-THA group demonstrated no significant side-to-side differences in any radiographic parameters, with consistently higher safe zone placement rates (92.7–94.5%). Operative time was longer for left-side M-THA compared to right-side (p = 0.041), while RA-THA showed no such disparity. Early clinical outcomes and complication rates were comparable between groups. Robotic-assisted THA effectively eliminates side-dependent disparities in acetabular cup placement attributable to surgeon handedness, ensuring high precision and consistency regardless of operative side. While short-term functional outcomes are similar, robotic assistance provides a standardized technical foundation for long-term implant survivorship and may serve as an equalizing tool in surgical training and procedural standardization.