Acetabular-only robot-assisted total hip arthroplasty is associated with lower surgeon stress index and perceived workload than conventional total hip arthroplasty: a prospective comparative cohort study

BACKGROUND: Robot-assisted THA (RATHA) has been associated with greater component-positioning accuracy, but surgeon workload during RATHA remains unclear. This study compared objective physiologic stress and perceived workload during conventional THA (CTHA) and RATHA. METHODS: This exploratory, hypothesis-generating study prospectively evaluated 60 elective primary THAs, comprising 30 CTHAs and 30 RATHAs, as repeated procedural observations from a single high-volume, fellowship-trained arthroplasty surgeon. All procedures were performed through a standardized posterolateral approach. RATHA used the MAKO system for acetabular preparation and cup implantation only. Intraoperative physiologic data were collected using a Hexoskin smart garment. Whole-case outcomes included heart rate, stress index, root mean square of successive differences (RMSSD), respiratory rate, minute ventilation, and energy expenditure rate. Perceived workload was assessed using the Surgery Task Load Index (SURG-TLX). Phase-specific stress index and RMSSD were analyzed across exposure, acetabular preparation, femoral preparation, and wound closure. RESULTS: Baseline patient characteristics were comparable between groups. Operative time was significantly longer during RATHA than CTHA (141.50 ± 30.76 vs 116.86 ± 21.88 min, p < 0.001). Despite this, RATHA was associated with a lower SURG-TLX composite score (adjusted mean difference, - 0.47; 95% CI - 0.85 to - 0.09; p = 0.039), with lower scores for task complexity and situational stress. Whole-case stress index was lower during RATHA (adjusted mean difference, - 2.52; 95% CI - 4.21 to - 0.83; p = 0.004), whereas the between-group difference in whole-case RMSSD was not statistically significant (geometric mean ratio, 1.35; 95% CI 0.98-1.86; p = 0.067). Heart rate, respiratory rate, minute ventilation, and energy expenditure rate did not differ significantly between groups. Phase-specific analysis showed lower stress index during RATHA in exposure, acetabular preparation, and femoral preparation, but higher stress index during wound closure. RMSSD was higher during RATHA in exposure and acetabular preparation. CONCLUSIONS: In this single-surgeon cohort, the acetabular-only RATHA workflow was associated with lower perceived workload and a lower mean whole-case stress index than the CTHA workflow despite longer operative time. These hypothesis-generating findings warrant validation in multisurgeon studies.