Improving Femoral Torsion Evaluation in Infants Through Analysis of Variability and Reliability in Two-Dimensional and Three-Dimensional Imaging Measurements of the Femoral Neck Axis

Abstract The femoral neck axis serves as a critical parameter in evaluating hip joint health, particularly in the pediatric population. Commonly used metrics for evaluating femoral torsion, such as the femoral neck-shaft and femoral anteversion angles, rely heavily on precise definitions of the position and orientation of the femoral neck axis. Current measurement methods employing radiographs and performing two-dimensional (2D) measurements on computed tomography (CT) scans are susceptible to errors due to their reliance on reader experience and the inherent limitations in 2D measurements. We hypothesized that utilizing volumetric data would mitigate these errors and enable more accurate and reproducible measurements of the femoral neck axis using the femoral anteversion and femoral neck-shaft angles. To test this hypothesis, we analyzed a historical collection of postmortem infant femoral and pelvic bones (28 hips) aged 0 to 6.5 months, with an average estimated age of 4.68 ± 1.80 months. Our findings revealed an average neck-shaft angle of 128.00 ± 4.92 deg and femoral anteversion angle of 35.56 ± 11.68 deg across all femurs, consistent with literature values. These measurements obtained from volumetric image data were found to be repeatable and reliable compared to conventional methods. Our study suggests that the proposed methodology offers a standardized approach for obtaining repeatable and reproducible measurements, thus potentially enhancing diagnostic accuracy and clinical decision-making in assessing hip developmental conditions in pediatric patients.