Journal of Clinical Medicine
Association of S2 Alar–Iliac Versus S1-Only Fixation with Spinopelvic Mobility and Acetabular Component Orientation in Total Hip Arthroplasty: A Standing–Sitting EOS Study
By Burak Abay, Meriç Enercan and Azmi Hamzaoğlu.
Abstract
Background
S2 alar–iliac (S2AI) fixation crosses the sacroiliac joint, unlike fixation terminating at S1, and may be associated with reduced spinopelvic mobility in patients undergoing total hip arthroplasty (THA). We compared spinopelvic mobility, femoropelvic reorientation, acetabular component orientation, and hip-specific function between S2AI and S1-only fixation.
Methods
This retrospective comparative cohort study included 60 patients undergoing THA after adult spinal fusion with S2AI (n = 30) or S1-only (n = 30) fixation. Standing and sitting EOS imaging at 1 year assessed changes in sacral slope (ΔSS) and pelvic–femoral angle (ΔPFA). Immediate postoperative CT measured static acetabular component orientation. Hip-specific function was assessed using the Hip Disability and Osteoarthritis Outcome Score (HOOS). Multivariable regression evaluated associations with ΔSS and HOOS.