Accuracy and Precision of Acetabular Component Position Does Not Differ Between the Anterior and Posterior Approaches to Total Hip Arthroplasty With Robotic Assistance: A Matched-Pair Analysis.

Background: Deviation from planned component placement with robot-assisted total hip arthroplasty (RA-THA) may differ based on surgical approach. The purpose of this study was to compare radiographic accuracy and precision of acetabular component position using RA-THA with the direct anterior approach (DAA) or posterior approach (PA).

Methods: Between 2016 and 2019, 134 PA RA-THA patients were matched to 134 DAA RA-THA patients based on age (±10 years), body mass index (±5 kg/m), and sex (exact). Acetabular component position was assessed using (1) planned position on preoperative computed tomography, (2) intraoperative position, and (3) position on 6-week postoperative radiographs using the digital Ein Bild Röntgen Analyse system.

Results: Accuracy of acetabular component inclination in the PA cohort was lower than that in the DAA cohort (PA: 4.3° ± 2.8° vs DAA: 3.1° ± 2.4°,  = .001). Inclination precision was not statistically different (PA: 3° ± 2.4° vs DAA: 2.5° ± 1.8°,  = .071). Anteversion accuracy was not statistically different (PA: 4.1° ± 3.7° vs DAA: 3.5° ± 2.5°,  = .091). Acetabular component anteversion was more precise with DAA (PA: 4.1° ± 3.7° vs DAA: 2.9° ± 2.0°,  = .001). Radiographic outliers (anteversion or inclination was >10° or <-10° from the planned target) were significantly more prevalent in the PA cohort than in the DAA cohort (12 vs 3,  = .016).

Conclusions: The acetabular component can be positioned with excellent precision and accuracy when using RA-THA regardless of approach. Although the DAA resulted in a slight increase in precise placement of cup anteversion and more accurate placement of cup abduction with fewer outliers, these small differences may not be clinically meaningful.