Robotic-Arm Assisted Direct Anterior Total Hip Arthroplasty; Improving Implant Accuracy

The aim of this study was to investigate the accuracy of implant position of robotic-arm assisted total hip arthroplasty (THA) via the direct anterior approach (DAA).All patients who underwent robotic-arm assisted DAA THA (MAKO Surgical Corp., Ft. Lauderdale, Florida) from November 2018 to January 2020 were prospectively followed up. Pelvis indices (limb length discrepancy, femoral and hip offset, implant inclination, and anteversion), surgical duration, length of stay, and complications were recorded. To further evaluate the accuracy of robotic-arm assisted THA, patients who underwent manual DAA THA by the same surgeon were match-paired with the study group.Twenty-five patients underwent robotic-arm assisted DAA THR. Limb length discrepancy was restored to 0.1mm (±3.4mm) from 10.0mm (±6.4mm) postoperatively. Preoperatively, the difference in femoral offset was 5.1mm (±5.1mm), and this was corrected to 1.9mm (±6.5mm) postoperatively. Nine cases had target inclination of 40° and mean inclination achieved was 40.7° (±0.9°). Sixteen cases had target inclination of 45° and mean inclination achieved was 45.3° (±1.0°). Mean anteversion was 19.5° (±2.4°). Propensity matched analysis showed that the root mean square errors for manual cup implantation compared to the robotic-arm assisted group was 2.3 times higher for anteversion and 6.3 times higher for inclination. Fourteen (56%) of the cups were within Callanan safe-zone and 18 (72%) within Lewinnek safe-zone in the manual group compared to 18 (72%) and 25 (100%), respectively, in the robotic-arm assisted group.Combining the muscle-sparing technique of DAA with the improved implant placement with the robotic-arm assisted platform is a promising solution to improving THA outcomes.