Minimum 5-Year Outcomes of Robotic-assisted Primary Total Hip Arthroplasty With a Nested Comparison Against Manual Primary Total Hip Arthroplasty: A Propensity Score–Matched Study

BACKGROUND: Robotic-assisted technology has been a reliable tool in enhancing precision and accuracy of cup placement in total hip arthroplasty (THA). Still, questions remain on the clinical benefit of this technology. METHODS: The purposes of the ongoing study were (1) to report on minimum 5-year outcomes in patients who underwent robotic-assisted primary THA (rTHA), (2) to compare those outcomes to a propensity score-matched manual primary THA (mTHA) control group, and (3) to compare radiographic measures between the groups regarding acetabular cup placement. Prospectively collected patient data were retrospectively reviewed for primary THA recipients during June 2008 to July 2013. Patients with minimum 5-year follow-up for Harris Hip Score, Forgotten Joint Score-12, Veterans RAND-12 Mental, Veterans RAND-12 Physical, 12-Item Short Form Survey Mental, 12-Item Short Form Survey Physical, visual analog scale, and satisfaction were included. Patient-reported outcomes, cup placement, and revision rate of the rTHA group were compared with those of a propensity score-matched mTHA control group. RESULTS: Sixty-six rTHAs were matched to 66 mTHAs. The rTHA group reported significantly higher Harris Hip Score, Forgotten Joint Score-12, Veterans RAND-12 Physical, and 12-Item Short Form Survey Physical (P < 0.001, P = 0.002, P = 0.002, P = 0.001). The acetabular implant placement by rTHA had a 9 and 4.7-fold reduced risk of placement outside the Lewinnek and Callanan safe zones, respectively (relative risk, 0.11 95% confidence interval, 0.03 to 0.46; P = 0.002; relative risk, 0.21 95% confidence interval, 0.01 to 0.47; P = 0.001). In addition, rTHA recipients had lesser absolute values of leg length discrepancy and global offset (P = 0.091, P = 0.001). CONCLUSIONS: Patients who received rTHA reported favorable outcomes at minimum 5-year follow-up. Furthermore, in comparison to a propensity score pair-matched mTHA group, rTHAs reported higher patient-reported outcome scores and had 89% reduced risk of acetabular implant placement beyond the Lewinnek safe zone and 79% reduced risk of placement beyond the Callanan safe zone. LEVEL OF EVIDENCE: Level III.