EP1.52 Gait Asymmetry Patterns in Femoroacetabular Impingement: Association with Operative-Stance Acetabular Coverage Reclassification

Abstract Background Patients with femoroacetabular impingement (FAI) frequently demonstrate gait asymmetry, including pelvic drop and altered stance phase. Whether these gait changes associate with dynamic reclassification of acetabular coverage during the operative hip’s load-bearing phase has not been investigated. We hypothesized that FAI patients, whose dynamic lateral center-edge angle (LCEA) differs from static LCEA, will demonstrate gait asymmetry and spend less time on the operative side. Methods Gait parameters were extracted from 101 FAI patients (38 male / 63 female; mean age 31.1 ± 11.7 years) using motion capture at 60 Hz. A dynamic LCEA was computed for each frame by adding coronal pelvic drop to static LCEA and classified as dysplastic <20°, borderline 20–25°, normal 25–40°, or over-covered ≥40°. A gait symmetry index (GSI) was calculated as the normalized stride-duration difference. Operative-stance reclassification was defined as any frame in which dynamic LCEA classification differed from static baseline. Results Borderline patients (n = 17) trended toward prolonged operative-limb stance (1.7 s [SD 0.8] vs. 1.4 s [SD 0.5] contralaterally; paired t = 1.3, p = 0.23; Wilcoxon p = 0.46). Normal patients (n = 68) showed near-symmetric gait (60.8% vs. 59.6%), and over-covered patients (n = 14) showed fully symmetric gait (60.7% vs. 60.8%). Twenty-five patients (26.6%) demonstrated both operative-stance reclassification and GSI exceeding 5%, representing a subgroup in whom dynamic coverage changes coincided with observable gait asymmetry. Conclusion Gait asymmetry varies by dynamic coverage classification, with borderline patients tending to spend more time on their operative limb — opposite the expected antalgic response, possibly reflecting prolonged tolerance of dynamic undercoverage. Over-covered patients showed no such asymmetry. Combining operative-stance reclassification with gait-symmetry analysis identifies a subgroup (~27%) whose functional hip biomechanics differ meaningfully from their static classification and who may warrant closer follow-up.