FP14.7 Proposing the Femoroacetabular Contribution Index Obtained by EOS Edge Measurements in Three Positions: Association with One-Year Outcomes Following Hip Arthroscopy for FAIS

Abstract ICLA14 - The Extra-Articular Masterclass: Endoscopic Repairs, Ischiofemoral Fixes, and Complex Alignment, Auditorium A (BMCC Level 1), October 9, 2026, 14:00 - 16:00 Purpose Femoroacetabular impingement syndrome (FAIS) is a motion-related disorder in which pelvic compensation may influence symptoms and outcomes. To quantify the contribution of femoroacetabular mobility (hip mobility HM) to the total lumbopelvic-femoral motion arc (Gobal Mobility GM), we developed a Femoroacetabular Contribution Index (FAC). This study evaluated whether FAC was associated with intraoperative findings and 1-year outcomes after hip arthroscopy for FAIS. Methods This retrospective cohort included patients who underwent primary hip arthroscopy for FAIS with preoperative EOS Edge acquisitions in standing, sitting, and deep-flexion positions, extracting measurements of sacral slope angles and sacrofemoral angles. FAC is the ration of HM to GM calculated by dividing the sacrofemoral angle arc (giving the HM) by the sum of the sacrofemoral angle arc and sacral slope arc (giving the GM) across the three positions. Higher FAC indicated hip-dominant motion and lower pelvic contribution. The primary outcome was 1-year postoperative Proms, including iHOT-12 and delta iHOT-12, NAHS, mHHS. Secondary outcomes included intraoperative labral/chondral findings, one year residual pain and satisfaction. Results 43 hips were included; 34 had available 1-year Proms. In the 34-patient series, mean FAC was 71.5% (SD 5.8%; mean ± 2 SD: 60.0%–83.0%). Higher FAC was associated with lower iHOT-12 (rho=-0.411, p=0.0157), lower NAHS (rho=-0.519, p=0.0017), lower mHHS (rho=-0.463, p=0.0058), greater hip residual pain (rho=0.527, p=0.0014), and lower satisfaction (rho=-0.403, p=0.0181). Each 0.10 increase in FAC was associated with an 18.7-point decrease in iHOT-12 (p=0.0012), with persistent associations in exploratory models adjusted separately for baseline iHOT-12, age, alpha angle, LCEA/VCE, Tonnis grade, and cartilage lesion. FAC was not significantly associated with delta iHOT-12 or intraoperative labral/chondral findings. Conclusion Higher FAC, reflecting femoroacetabular-dominant motion with reduced pelvic contribution, was associated with inferior 1-year outcomes and greater residual pain after hip arthroscopy for FAIS. Deep-flexion EOS Edge assessment may provide functional information beyond conventional radiographic morphology.