Early national comparison of robotic versus conventional hip replacements for arthritis using National Joint Registry data: target trial emulation study

Abstract Objectives To evaluate the early comparative effectiveness of robotic versus conventional total hip replacement (THR) in the UK. Design Target trial emulation study. Setting Public and private hospitals using data from the National Joint Registry of England, Wales, Northern Ireland, the Isle of Man, Guernsey, and Jersey. Participants 666 283 THRs performed between 2018 and 2024; 656 080 were conventional THRs and 10 203 were robotic THRs. Main outcome measures Five year THR implant survival (mean 2.5 year follow-up), all cause revision risk, cause specific revision risk, malpositioning revision risk, intraoperative complications, and patient survival up to five years. Kaplan-Meier survival analysis, Cox proportional hazards regression, and Fine and Gray models were used. Propensity score matching created comparable treatment groups to estimate the average treatment effect in the treated population. Results The five year implant survival of the matched conventional and robotic THR groups was 98.8% (95% confidence interval (CI) 98.6% to 99.0%) and 98.8% (CI 98.3% to 99.1%), respectively, with no difference in revision risk between groups (hazard ratio 0.96, 95% CI 0.75 to 1.22; P=0.73). Cause specific revision risk and intraoperative complication risks did not differ between groups. However, a significantly lower risk of revisions related to implant malposition (dislocation, leg length discrepancy, and malalignment) was observed in the robotic group (hazard ratio 0.53, 95% CI 0.30 to 0.93; P=0.03). The five year patient survival of the matched conventional and robotic THR groups was 96.3% (95% CI 95.8% to 96.8%) and 96.2% (95.2% to 97.0%), respectively, with no difference in all cause mortality risk (hazard ratio 1.12, 95% CI 0.95 to 1.34; P=0.17). Conclusions No significant differences were found in overall THR or patient survival, cause specific revision, or intraoperative complication risks between robotic and conventional groups. Robotic THR was associated with a lower revision risk from causes related to implant malpositioning. However, the possibility of unmeasured and residual confounding cannot be ruled out owing to the observational design. These results highlight the importance of careful evaluation of robotic technology in publicly funded healthcare systems because of the substantially higher capital and procedural costs.