Anterior Inferior Iliac Spine Morphology: Comparison of Symptomatic Hips With Femoroacetabular Impingement and Asymptomatic Hips.

The objective of our study was to compare anterior inferior iliac spine (AIIS) morphology in symptomatic hips with femoroacetabular impingement (FAI) and in asymptomatic hips, determine the prevalence of impingement morphology in patients with a radiographic "crossover" sign, and identify potential risk factors for having impingement morphology. For this retrospective study, we identified consecutive symptomatic hips with FAI (n = 54) and asymptomatic hips (n = 35) in patients who underwent CT from 2015 to 2017. Two radiologists blindly and independently evaluated 3D CT images of each hip and graded the AIIS morphology according to the Hetsroni classification scheme. The prevalence of AIIS morphology types was calculated. Associations of AIIS morphology types with symptoms and the crossover sign were evaluated with a chi-square test. A multivariable logistic regression determined risk factors for abnormal AIIS morphology (i.e., type 2 or 3). There was no difference in the prevalence of AIIS morphology types for symptomatic hips with FAI versus asymptomatic hips (p = 0.44) or for hips with a positive versus those with a negative crossover sign (p = 0.21). There was moderate interobserver agreement (κ = 0.44) and good-to-excellent intraobserver agreement (κ = 0.67 and 0.90) for grading AIIS morphology. Age, sex, femoral version, acetabular version, alpha angle, lateral center edge angle, and the crossover sign were not significant risk factors for abnormal AIIS morphology in patients with FAI (p = 0.11-0.79). There is no difference in AIIS morphology between symptomatic hips with FAI versus asymptomatic hips or between hips with and those without the radiographic crossover sign. Age, sex, and other FAI parameters are not risk factors for developing AIIS impingement morphology.