Robotic arm–assisted total hip replacement: Early experience in Hong Kong

Abstract

Introduction: Acetabular cup placement is crucial in preventing complications and ensuring implant longevity in total hip arthroplasty (THA). Robotic arm assistance enables accurate acetabular bone removal and allows precise cup placement. This study analyses the early clinical experience. Methods: All robotic arm–assisted Mako THAs performed from 1 February 2019 to 9 July 2020 in Queen Mary Hospital were analysed. Posterior approach with robotic arm–assisted acetabular reaming and cup impaction were performed, followed by intraoperative verification with software. Postoperative radiographs, intraoperative verification and preoperative planning were compared for inclination and anteversion angles. Harris hip scores, complications and mortality were documented. Results: 52 robotic arm–assisted THAs were performed in 45 patients. Mean age was 63 years and mean BMI was 24.6. Most patients suffered from osteoarthritis (18) followed by avascular necrosis (15). Mean surgical time was 125 minutes with learning curve of nine cases. Average follow-up was 9.4 months. Mean Harris hip scores improved from 46 before surgery to 90 at 6 months after surgery (p<0.001). All components were well fixed upon latest follow-up. No complications including loosening nor dislocations occurred although one patient died 8 months after surgery from medical cause. Intraoperative verification of robotic arm–assisted cup position correlated strongly with preoperative planning in both inclination (r=0.7, p<0.001) and anteversion (r=0.82, p<0.001). Postoperative radiographic inclination (r=0.38, p=0.01) and anteversion (r=0.37, p=0.02) correlated moderately with preoperative plan. Postoperative analysis showed 96% of robotic positioned cups fell within Lewinnek’s safe zone (inclination 30°-50°, anteversion 5°-25°). Conclusion: Robotic arm–assisted THA enables accurate cup placement with promising early clinical results.