Age- and gender-specific variations of the epiphyseal tilt and epiphyseal angle in adolescents without hip pathology

PURPOSE: To determine age-and gender-dependent variation of epiphyseal tilt and epiphyseal angle using CT in adolescents without hip pathology. METHODS: Pelvic CT scans were obtained in 132 adolescents for evaluation of abdominal pain. Radially oriented planes around the femoral neck were reformatted and the epiphyseal tilt and angle were measured in the anterior, anterosuperior and superior planes. Variations in the tilt angle and epiphyseal angle were assessed by age group from 12 to 18 years and gender by using a linear mixed model analysis. RESULTS: The epiphyseal tilt did not change (p = 0.97) with increasing age. Male patients exhibited smaller tilt angle in the anterosuperior plane (p = 0.003) but no difference was detected in the anterior (p = 0.17) or superior (p = 0.06) planes. The epiphyseal angle decreased with increasing age in the anterior (p = 0.03), anterosuperior (p = 0.001) and superior (p < 0.001) planes in male patients, with no variation in female patients (p = 0.92). Male patients had larger epiphyseal angles in the anterior (p = 0.02), anterosuperior (p < 0.001) and superior (p = 0.002) planes compared with female patients. CONCLUSION: We found no age-specific variations in the epiphyseal tilt and no difference in the epiphyseal tilt in male and female patients in the superior and anterior plane. The epiphyseal angle was smaller in female patients, however, the epiphyseal angle decreased with increasing age in male patients which corresponds to an increase in epiphyseal extension. The reference values reported in this study may serve as additional information in the evaluation of adolescents with hip pain and as reference for future studies investigating slipped capital femoral epiphysis and femoroacetabular impingement development. LEVEL OF EVIDENCE: Level III Diagnostic Study