Establishing normative femoral morphology in the pediatric population using computed tomography

This study defines normal lower limb morphology in healthy children using computed tomography (CT) to distinguish normal variants from pathological deformities during lower limb growth. Our pilot study showed that measurements of femoral anteversion angle (FAA) and intracanal diameter (ICD) on CT were not feasible under age 6. CT scans were retrospectively analyzed in 172 patients (318 femurs) aged between 6 and 17. Measurements included FAA, ICD, and femoral antecurvatum. The distribution of the parameters according to age, gender, and side comparisons were evaluated. Mean FAA was 19.2 ± 10.4°. Girls had significantly higher mean FAA [23.5 ± 8.5° in girls vs. 18.1 ± 10.5° in boys (P < 0.001)]. Mean FAA showed a trend of decrease of around 50% as age increased. A total of 2.9% of the study population had femoral retroversion. Right-to-left side difference in FAA was more than 5° in 24.6%, and more than 10° in 3.33% of the study population. The mean ICD increased 56% as age increased. Girls had significantly lower mean ICD as compared with boys [8.7 ± 1.8 mm in boys vs. 7.3 ± 1.9 mm in girls (P < 0.01)]. Femoral antecurvatum did not change significantly throughout growth. This study provides CT-based normative data on femoral morphology (FAA, ICD, and femoral antecurvatum) in a healthy pediatric population aged 6-18 years. FAA showed a negative correlation with age. Girls had higher FAA but lower femoral antecurvatum and narrower ICD than boys. These findings should be confirmed in larger, longitudinal studies.