Utility of anterior wall of greater trochanter in predicting femoral anteversion angle: a three-dimensional computed tomography-based simulation study

Background The femoral anteversion angle is an important factor in performing surgery in the proximal part of the femur. Predicting the femoral anteversion angle based on the morphology of the proximal femur is clinically useful. The purpose of this study was to investigate whether an anatomical landmark can be used to predict the femoral anteversion angle intraoperatively. Materials and methods We analysed CT data obtained from 100 hips in 69 patients with osteonecrosis of the femoral head with no more than 2 mm collapse and no evidence of osteoarthritic changes. The measured variables were the femoral anteversion angle, the femoral neck-shaft angle, and the AW angle (defined as the angle between the femoral shaft axis and the tangential line of the anterior wall of the greater trochanter). The correlations between variables were also investigated. Multiple regression analysis by the forced input method was performed for the degree of femoral anteversion angle, using sex and the AW angle as explanatory variables. Results On CT, the mean femoral anteversion angle was 14.8 degrees +/- 10.8 degrees, the mean AW angle was 17.5 degrees +/- 8.0 degrees, and the mean femoral neck-shaft angle was 127.3 degrees +/- 5.4 degrees. There was a positive correlation between the femoral anteversion angle and the AW angle. The approximation equations based on the multiple regression analysis were as follows: male femoral anteversion angle = AW angle x 0.7 - 0.7 and female femoral anteversion angle = AW angle x 0.7 + 4.3. Conclusions Femoral anteversion angle can be predicted based on the AW angle of the greater trochanter.