Comparison of Postoperative Instability and Acetabular Cup Positioning in Robotic Assisted versus Traditional Total Hip Arthroplasty

BACKGROUND: Robotic-assisted total hip arthroplasty (R-THA) affords precision yet uncertain clinical benefits. This study compares dislocation rates and related revisions between R-THA and manual total hip arthroplasty (M-THA). Secondarily we evaluated cup position, patient-reported outcome measures (PROMs), and postoperative complications. METHODS: A three-surgeon cohort study was conducted on 2,247 consecutive patients (1724 M-THA and 523 R-THA) who received a primary THA between January 2014 and June 2020 at a single hospital. Demographics, PROMs, emergency department visits, readmissions, and 90-day complications were collected via the Michigan Arthroplasty Registry Collaborative Quality Initiative. Chart review yielded instability occurrence with average follow-up of 4 years. Multivariate regression analysis was performed and a sample of 368 radiographs including all dislocations were assessed. RESULTS: There were significantly lower rates of dislocation in R-THA (0.6%) versus M-THA (2.5%; Multivariate odds ratio 3.74, p \u3c .046). All cases of unstable R-THA were successfully treated conservatively, whereas 46% of unstable M-THA were revised for recurrent instability. Cup anteversion (25.6° ± 5.4° R-THA vs. 20.6° ± 7.6° M-THA) was greater and cup inclination (42.5° ± 5.3° R-THA vs. 47.0° ± 6.7° M-THA) was lower in the R-THA group (p \u3c .05). No significant differences were noted for demographics, PROMs, or other complications (p \u3e .05). CONCLUSION: R-THA resulted in less than one-fourth the dislocation rate compared to M-THA and no revision for instability. It was associated with no difference in PROMs or other early complications. The influence of R-THA on stability goes beyond simply cup positioning and deserves further study