Distribution of anterior inferior iliac spine morphology in patients with femoroacetabular impingement syndrome, developmental dysplasia of the hip, and asymptomatic controls: a retrospective cohort study.

Abstract

To compare the distribution of anterior inferior iliac spine (AIIS) morphology on three-dimensional computed tomography (3D-CT) among hips with femoroacetabular impingement syndrome (FAIS), developmental dysplasia of the hip (DDH), and an asymptomatic control cohort. In this single-center retrospective cross-sectional study, AIIS morphology was classified on 3D-CT using a four-subtype system. Asymptomatic control hips were selected from individuals undergoing abdominopelvic CT for non-orthopaedic indications, whereas FAIS and DDH hips were identified from patients evaluated for hip-preservation surgery. Lateral center-edge angle (LCEA) was measured on clinical anteroposterior pelvic radiographs or CT-derived anteroposterior digitally reconstructed radiographs, as applicable. AIIS morphology distributions were compared among groups using chi-square testing with post hoc pairwise analyses. Multivariable logistic regression was used to identify independent predictors of Type III morphology after adjustment for diagnostic group, LCEA, age, and sex. A total of 1,420 hips were analyzed, including 800 asymptomatic hips, 500 FAIS hips, and 120 DDH hips. AIIS morphology distribution did not differ significantly between the FAIS and asymptomatic cohorts. Type III morphology was identified in 9.2% and 9.3% of hips in these two groups, respectively. In contrast, the DDH cohort showed a significantly different distribution, with Type III morphology present in 60.0% of hips. On multivariable analysis, DDH remained the strongest independent predictor of Type III morphology (adjusted odds ratio, 7.99; 95% confidence interval, 3.33-19.14; P < 0.001). Static 3D-CT AIIS morphology did not distinguish FAIS hips from asymptomatic hips. In contrast, Type III morphology was markedly more common in DDH, suggesting that AIIS morphology should be interpreted in the context of acetabular coverage and the underlying hip disorder.