EP9.4 Imaging Adjustment for Pelvic Coronal Plane Kinematics During Gait: A Reliability Study of Femoral Head Coverage

Abstract Purpose Gait-related coronal pelvic motion may alter femoral head coverage but is not reflected in conventional static radiographs. Wearable inertial measurement units (IMUs) enable quantification of pelvic kinematics during walking, which can be used for standard imaging adjustment. It was hypothesized that femoral head coverage measurements obtained from adjusted standing pelvic radiographs would demonstrate high inter- and intra-rater reliability. Methods A prospective single-institutional hip preservation registry with 129 cases was screened for unilateral femoro-acetabular impingement syndrome (FAIS) cases, of which 10 patients (20 hips) were selected. The registry includes supine and standing radiographs and motion capture using IMUs. The coronal pelvic kinematics used during walking included contralateral peak pelvic drop and compensatory, ipsilateral femoral adduction. Both dynamic parameters were incorporated into standard standing pelvic radiographs through image adjustment. Two raters independently measured the lateral center-edge angle (LCEA), acetabular index (AI), femoro-epiphyseal acetabular roof index (FEAR), and extrusion index (EI) to determine inter- and intra-correlation coefficients (ICCs). Results The mean peak pelvic drop on the asymptomatic hip was 5.2° ± 1.6° (2.2° to 7.1°), with compensatory femoral adduction of -2.8° ± 5.1° (-13.8° to 4.2°) on the affected side. Inter-rater reliability had ICCs of 0.71 to 0.97 in the first round and 0.86 to 0.96 in the second round for femoral head coverage parameters on the adjusted radiographs, while intra-rater agreement showed ICCs ranging from 0.77 to 0.94 for rater 1 and 0.73 to 0.97 for rater 2. Discussion This study demonstrated high inter- and intra-rater reliability for adjusted radiographs that incorporated dynamic motion data to assess femoral head coverage during gait. Further research is needed to identify factors affecting coronal pelvic kinematics and to examine its possible surgical implications and effect on outcomes.