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

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.