Measurement of Femoral Neck Anteversion Angle in Children With Intoeing Gait by Using Femoral Plain Radiographs: A Retrospective Observational Study

BACKGROUND: Increased femoral neck anteversion is a common cause of intoeing gait in children. Computed tomography (CT) is the reference standard for measuring femoral anteversion; however, its use is limited by radiation exposure. This study evaluated the agreement between femoral neck anteversion angle (FAA) measurements obtained using standardized plain radiography and CT. METHODS: Data from patients aged 5 to 12 years with an intoeing gait who underwent both femoral CT and standardized anteroposterior and lateral radiography were retrospectively analyzed. FAA measurements were calculated from biplanar radiographs using a geometric method and compared with CT measurements. Agreement between the 2 methods was assessed using a paired test, Pearson correlation coefficients, and Bland-Altman analysis. RESULTS: Eighteen paired limb measurements were included. The mean FAA measured using radiography was 32.8±6.7 degrees, whereas the mean FAA measured using CT was 31.8±7.5 degrees. The mean difference was 1.0±1.7 degrees (P=0.020). Reliability was excellent for both measurement methods. The Bland-Altman analysis revealed a mean bias of 1.0 degrees, with limits of agreement ranging from -2.3 to 4.3 degrees, without evidence of proportional bias. CONCLUSIONS: Standardized biplanar radiography demonstrated close agreement with CT in assessing femoral anteversion. Although a significant difference was observed between the 2 methods, its magnitude was small and unlikely to be clinically meaningful, supporting the use of standardized plain radiography as an alternative in clinical practice. LEVEL OF EVIDENCE: Level IV-case series.