Body mass index and robotic-assisted total hip arthroplasty: current evidence, technical challenges, and clinical...

Higher body mass index (BMI) can increase the technical difficulty of total hip arthroplasty (THA), but whether robotic assistance preserves surgical accuracy in patients who are overweight or obese remains uncertain. This critical review evaluated current evidence regarding BMI-related radiographic, clinical, perioperative, and safety outcomes following robotic-assisted THA. A structured search of MEDLINE/PubMed and ClinicalTrials.gov was conducted through 8 September 2026 and supplemented by targeted citation checking. Owing to substantial clinical and methodological heterogeneity, findings were synthesised narratively without meta-analysis. Eight directly relevant studies, comprising one randomised trial and seven non-randomised studies, were included. Evidence from robotic-assisted THA cohorts did not demonstrate a clear deterioration in acetabular component-positioning accuracy with increasing BMI. Comparisons involving patients who are overweight or obese generally favoured robotic assistance over manual THA for target-zone achievement and restoration of leg length or centre of rotation, whereas patient-reported outcomes (PROMs) and complication rates showed no consistent statistically significant differences; however, the available studies were insufficiently powered to detect differences in uncommon complications, and the absence of significant differences should not be interpreted as evidence of equivalence. Robotic-assisted procedures were generally associated with longer operative times. Interpretation was limited by heterogeneous BMI thresholds, robotic platforms, surgical approaches, radiographic targets, and follow-up durations, together with sparse reporting of BMI-by-treatment interaction analyses. Robotic assistance may therefore help maintain radiographic execution in technically demanding patients with higher BMI; however, the available evidence does not establish that BMI modifies its comparative effectiveness over manual THA. Improvements in PROMs and cost-effectiveness, as well as reductions in complication and revision rates, remain unproven. Prospective studies using harmonised radiographic endpoints and prespecified BMI-by-treatment interaction analyses are required.