Robotic-arm assistance in revision total hip arthroplasty improves the accuracy of acetabular component positioning: a cadaver-based study

INTRODUCTION: Acetabular component positioning is a key factor for stability, impingement, wear, and biomechanics in revision total hip arthroplasty (THA). However, anatomic distortion and previous implants may complicate positioning. Although evidence on computed-tomography (CT)-based robotic assistance in revision THA is limited, its planning features and precision may improve surgical plan execution. This study aimed to measure the precision and accuracy of acetabular component positioning of revision robotic-arm assisted total hip arthroplasty (RA-THA) compared with a published manual primary total hip arthroplasty (M-THA) benchmark for: (a) acetabular inclination; (b) acetabular version; and (c) center of rotation (COR), with comparison by surgeon case volume. MATERIALS AND METHODS: There were seven cadavers (nine hips) that previously underwent primary THA revised with RA-THA by independent surgeons with varying primary RA-THA case volumes, surgical approaches, and acetabular component types. Due to surgical protocol deviations, two hips were excluded leaving seven hips from six cadavers. Pre- and postoperative CT scans were compared to calculate absolute error for inclination, version, and COR; normality was established with the Anderson-Darling test and two-variance tests assessed differences in standard deviations (α = 0.05). Mean differences between cadaver-based revision RA-THA and published M-THA values were compared with Welch's t-test for superiority (α = 0.05). Effect sizes were reported as mean differences with 95% upper bounds and sensitivity analyses were performed given the fixed sample size. RESULTS: Revision RA-THA demonstrated significantly greater accuracy for acetabular inclination (2.5 ± 1.9° versus 7.2 ± 3.2°, P = 0.008) and version (2.2 ± 1.6° versus 7.8 ± 4.6°, P = 0.014), and significantly greater precision for acetabular version (P = 0.023) compared with M-THA. There was adirectionally lower error for COR compared with M-THA. Mean error reductions were 5.7° for version and 4.7º for inclination with 95% upper bounds of -1.9 for both version and inclination. Low RA-THA surgical volume corresponded with the highest absolute error for shell inclination (5.5º) and version (5.0º), though values remained below published M-THA averages. CONCLUSIONS: Revision RA-THA reduced error in both acetabular inclination and acetabular version, and variability in acetabular version relative to the M-THA benchmark. Although these results relate only to technical performance, accurate acetabular positioning in clinical practice is an important factor in reducing the risk of malposition-related complications in revision THA.