Femoral anteversion: estimation by 3D modelling.

Femoral anteversion is the inclination of the femoral neck axis with reference to the tangent plane of the distal femur. For estimating femoral anteversion, following three major parameters are required; the neck axis, the long axis, the knee axis. Conventional methods on the basis of 2D images are ambiguous to determine these major axes. As the femur has a complex 3 dimensional structure, the 3 dimensional model should be applied for accurate and reliable measurement of femoral anteversion. In this paper, we model femur and define three parameters. The neck axis is defined from the femoral head and neck model. The long axis is determined from the cylindrical model of the femoral shaft. The knee axis is also determined from the model of femoral condyles. According to the definition of the femoral anteversion, the femoral anteversion is efficiently estimated from these models. 30 specimens were tested by conventional 2D imaging method, 3D imaging method which was developed by authors and the new 3D modelling method. The study provides accurate, fast and human factor free measurement for femoral anteversion.