Accuracy, efficiency, and clinical outcomes of a pinless CT-Free, robotic arm-assisted total hip replacement system

Background Fluoroscopic-based robotic-assisted total hip arthroplasty (raTHA) platforms expose patients to less radiation than CT-based raTHA, however, the accuracy of these novel raTHA systems requires further investigation. The purpose of this study was to investigate the accuracy, efficiency, and early post-operative clinical outcomes of a pinless, fluoroscopic-based raTHA system. Methods A retrospective review of a single surgeon’s first 50 raTHA cases using the direct anterior approach (DAA) was conducted. Accuracy of acetabular component placement was determined by analysing the final planned target and post‐operative supine anteroposterior (AP) pelvic radiographs. Mean absolute differences (MAD) between target and post-operative radiographs were computed for cup inclination and anteversion, and the percentage of cases within the Lewinnek Safe Zone was calculated. To assess efficiencies in adoption, cumulative summation (CUSUM) analysis was performed using operative times and robotic timestamps to compare between learning and proficiency phases. Hip Disability and Osteoarthritis Outcome Score-12 (HOOS-12) and Oxford Hip Score (OHS) were collected pre-operatively and up to one-year post-operative. Results There were no significant (p=0.419) differences between targeted and radiographic cup inclination (41.8±1.5 vs. 42.3± 4)) or anteversion (15.9±1.3 vs. 15.2±3.0, p = 0.121). The raTHA MAD for inclination and anteversion were 3.6±2.7° and 2.4±1.8° respectively, and the percentage of cases within the Lewinnek Safe Zone was 96% (48/50). CUSUM analysis revealed an initial learning curve of 25 cases, with significantly shorter operative times in the proficiency compared to learning phase (65.6±7.9 vs. 72.4±12.7 min, p=0.028), and without significant differences in accuracy between phases. Both HOOS-12 and OHS significantly (p<0.0001) improved between pre-operative and one-year post-operative. Conclusion The results of this study demonstrate that use of a pinless, fluoroscopic-based raTHA system for DAA THA demonstrates high accuracy and reproducibility of acetabular cup placement with an initial learning curve of 25 cases.