Anterior approach and robotic assistance associated with shorter operative times and lower transfusion requirements in conversion total hip arthroplasty

BACKGROUND: This study aims to describe a cohort of patients who underwent conversion to total hip arthroplasty (THA), comparing surgical approach and robotic assistance. METHODS: Patients ≥ 18 years who underwent conversion to THA between January 1, 2015 and May 6, 2024, were retrospectively reviewed, and additionally contacted via telephone for updated patient reported outcome measures (PROMs), including the Hip Disability and Osteoarthritis Outcome Score, Joint Replacement (HOOS, JR) questionnaire. Surgical approach and robotic assistance were per surgeon preference, with consideration for the approach of the previous hip surgery. Descriptive statistics were calculated, and continuous variables analyzed using the Student's T-Test, the Wilcoxon Ranked Sum Test. Categorical variables were compared using Chi-Squared Tests and Fisher's Exact Tests, and outcomes analyzed with logistic regression in R statistical software. RESULTS: 83 patients met inclusion (53% anterior approach; 26.5% robotic assistance). Conversion via anterior approach demonstrated shorter operative times than posterior (by 45.9 min; p < 0.001), in addition to fewer postoperative transfusions (22.7% vs. 53.8%; p = 0.006). Length of stay (LOS), and fluoroscopy time were not significant. When stratified by previous surgery 37 patients were converted from prior intramedullary nail, 16 via the anterior approach. Mean operative time remained shorter (p = 0.003) and transfusion remained less (p = 0.015) compared to posterior conversion in this subset. Robotic assistance was associated with shorter operative times (by 44.9 min p < 0.001), and shorter LOS (p < 0.001). Zero robotic-assisted patients required transfusion within 24 h postoperatively compared to 50.8% of non-robotic cases (p < 0.001), although transfusion risk was not significant considering approach or robotic assistance after multivariable regression controlling for preoperative hemoglobin. PROMs were equivocal between compared groups (mean HOOS Jr 11.0 ± 5.1, response rate 42.2%). CONCLUSION: Conversion THA demonstrates acceptable outcomes, with documented overall improvements in postoperative function. The anterior approach and robotic assistance were associated with significantly shorter surgical times, and less risk of transfusion, potentially demonstrating some advantage in this conversion scenario, although patient selection may have also influenced outcomes.