TP5.1 Acetabular Over-Coverage Predicts Revision After Femoroacetabular Impingement Surgery: Association of Static and Dynamic Lateral Center-Edge Angle Classification with Reoperation Risk

Abstract Background Revision after primary hip preservation surgery for femoroacetabular impingement (FAI) is commonly regarded as treatment failure, yet whether radiographic patterns of acetabular coverage — particularly over-coverage — predict revision remains underexplored. We hypothesized that dynamic lateral center-edge angle (LCEA) classification during gait would outperform static radiographic classification in stratifying revision risk. Methods Data from 101 FAI patients (38 male / 63 female; mean age 31.1 ± 11.7 years; mean BMI 26.0 ± 4.8 kg/m2) who underwent primary hip arthroscopy for FAI were reviewed. Static LCEA was classified as dysplastic <20°, borderline 20–25°, normal 25–40°, or over-covered ≥40°. Dynamic LCEA was computed by adding coronal pelvic tilt during walking to static LCEA. Associations with revision were assessed using Welch’s t-test, Mann–Whitney U, Chi-square, Fisher’s exact, Cohen’s d, and Cramér’s V tests. Results Twenty-three of 101 patients (22.8%) underwent revision. Mean static LCEA was higher in revision patients (36.7 ± 7.0° vs. 32.0 ± 6.2°; Δ = 4.7°; Welch t = −2.9, p = 0.007; Cohen’s d = 0.7). Revision rates increased progressively across static LCEA classification groups: Borderline 1/17 (5.9%), Normal 16/69 (23.2%), and Over-coverage 6/15 (40.0%)(Chi2 = 5.3, p = 0.07, Cramér’s V = 0.2). The same pattern held for dominant dynamic classification during walking (Over-coverage 4/11, 36.4%; Normal 14/70, 20.0%; Borderline 1/11, 9.1%; Dysplasia 0/2, 0.0%) and operative-stance (Over-coverage 4/11, 36.4%; Normal 13/69, 18.8%; Borderline 2/12, 16.7%; Dysplasia 0/2, 0.0%), though neither static nor dynamic LCEA based measurements reached significance. Mean and median dynamic LCEA differences were non-significant (Δ = +2.7°; p > 0.12; Cohen’s d = 0.4). Revision patients spent approximately twice as much gait time in the over-coverage band (24.0% vs. 12.3%). Conclusion Both static and dynamic LCEA exhibited the same directional pattern in association with revision risk; however, static LCEA approached significance and showed a stronger association. Over-coverage (LCEA ≥40°) carried a roughly doubled revision rate relative to normal coverage, while only 1 of 17 borderline patients was revised. Dynamic classifications preserved the rank ordering but its detailed effect on prediction of revision risk needs clarification in larger studies.