Characterization of hip morphology phenotypes in individuals with femoroacetabular impingement syndrome with cam morphology: data from the PhysioFIRST trial

OBJECTIVE: To characterize different hip morphology phenotypes in individuals with femoroacetabular impingement (FAI) syndrome with cam morphology. MATERIALS AND METHODS: Supine pelvic anterior‐posterior radiographs from 119 hips from 119 individuals diagnosed with FAI syndrome with cam morphology from a RCT were analysed. The lateral center edge angle (LCEA), Wiberg center edge angle (W‐CEA), global retroversion, protrusio acetabuli, and femoral neck shaft angle (FNSA) measures were assessed independently by two raters. Criteria from the Lisbon Agreement on FAI imaging were used to characterize different hip morphology phenotypes based on overcoverage, undercoverage, retroversion and femoral orientation. Radiographic measure's reliability was calculated using intraclass correlation coefficients and kappa statistic. RESULTS: Reliability for all measurements ranged from good to almost perfect agreement. Global retroversion of the acetabulum was percent in 39% of the participants. Based on the W‐CEA, 9% of participants had acetabular undercoverage and 9% had overcoverage, while the LCEA identified 5% with undercoverage and 17% with overcoverage. Coxa valga was present in 27% of participants, with only one participant having coxa vara. No participants had protrusio acetabuli. Women had a slightly higher prevalence of coxa valga than men. CONCLUSION: Close to 40% of patients with FAI syndrome with cam morphology also displayed pincer morphology by acetabular retroversion. The prevalence of pincer morphology, based on the W‐CEA and LCEA measures was low, indicating that isolated use of these parameters may lead to underdiagnosis of pincer morphology. The prevalence of hip dysplasia determined by the W‐CEA and LCEA measures was low, ranging from 2 to 5%.