Comparison of Femoral Anteversion Measurement in 2 and 3 Dimensions

Femoral neck anteversion is usually measured on the 2-dimensional (2D) images on CT slices. The 3D method uses 3-dimensional model of the femur reconstructed from CT scan images. The aim of this study was to compare these two methods of measurement of femoral ante-version. In a retrospective study، CT scans of 40 patients (6 men، 34 women) of a teaching hospital in Tehran-Iran were included. Both methods use the same anatomical landmarks، i. e. center of femoral head، femoral neck axis and posterior apex of the femoral condyles. In the 3D method، anteversion angle was measured on a plane perpendicular to the anatomical axis of femur. Whereas in the 2D method the measurement is performed on CT scan slices. Mean anteversion was found to be 9. 8 for the 2D and 16. 11 for the 3D method. Bland-Altman plot shows that the difference between the two methods is significant. This difference between 2D ad 3D measurement of femoral anteversion may be depend on the level of the selected CT slices، patients positioning during CT examination، and the impact of the deformity. The 3D method eliminates obvious sources of error، namely identifying landmarks and individual orientation of femur. Due to the lack of any gold standard there is a need to further review and study the measurement of this angle.