Normative metrics and sex-specific differences in 3D acetabular morphology in asymptomatic young adults: implications...

Radiographs do not entirely capture the complexity of acetabular morphology. The purpose of this study was to establish normative three-dimensional (3D) acetabular morphology in young adults without hip disease and identify sex-specific differences in acetabular coverage. We analysed 3505 hips from 1856 asymptomatic subjects aged 18-25; 48% were female (n = 890), who had undergone pelvic computed tomography (CT) scans for abdominal pain. We used a custom software to automatically segment the CT data and create 3D models. The centre-edge angle (CEA) and acetabular rim lateral extension (ARLE) were assessed at various clock-face positions around the acetabulum and sex-related differences were calculated. Females had greater acetabular coverage posteriorly, with higher mean CEA values at 9 o'clock (12° versus 9°; P < .001) and 10 o'clock (23° versus 20°; P < .001) and higher ARLE at 9 o'clock (0.54 versus 0.51; P < .001), 10 o'clock (0.63 versus 0.60; P < .001), and 11 o'clock (0.71 versus 0.70; P < .001). Males exhibited greater superior and anterior coverage, with higher CEA values at 12 o'clock (36° versus 34°; P < .001), 1 o'clock (28° versus 26°; P < .001), and 2 o'clock (4° versus 2°; P < .001) and higher ARLE at 12 o'clock (0.74 versus 0.73; P < .001), 1 o'clock (0.67 versus 0.66; P < .001), and 3 o'clock (0.25 versus 0.24; P = .01). Using automatic computational 3D modelling we found greater posterior acetabular coverage in females, whereas males exhibited more extensive superior and anterior coverage. Detailed 3D mapping of acetabular morphology may enable the development of standardized, sex-specific models to improve diagnosis and guide surgical planning of acetabular dysplasia and pincer femoroacetabular impingement.