Measuring anteversion in the femoral neck from routine radiographs

Abstract

Purpose: To describe a new method for measuring femoral neck anteversion (FNA) that requires only one lateral radiograph of the knee in addition to routine radiographs of the hip for evaluation of total hip replacement; and to compare the proposed method with FNA measurement by means of 3D CT.

Material and Methods: In 18 femoral specimens, radiographic examinations of the hip and knee, in three different rotational positions, and one CT examination were made, and the measurements of FNA were compared. Similarly, in 38 patients with 40 total hip replacements, measurements from routine radiographic examinations of the hip and knee and from CT examinations were compared. The accuracy and reproducibility of the FNA measurements produced by this proposed method were calculated.

Results: Accuracy and reproducibility were 2° and 2° for the proposed method in the femoral specimen study, and accuracy was 4° in the hip patient study. The proposed method had a minor flaw that was caused almost solely by differences in knee size at inward rotation of the femur.

Conclusion: FNA measurement can be made from a routine radiographic examination of the hip and a lateral view of the knee. This method achieves an acceptable level of accuracy and reproducibility.