Fig. (1) The 3D calculation of the femoral offset is schematically
shown in a 3D-reconstruction of the pelvic bone and the proximal
femur produced by the Amira 4.1.1 (Amira®, San Diego, California,
USA) software package. Ellipses have been fitted automatically
into the medullary canal (shown here for the right side). The
femoral axis was calculated by the best line of fit through the
ellipse-center points. A virtual plane was created containing the
femoral axis and the center of the femoral head. The femoral offset
was calculated as the distance between the femoral axis and the
femoral head center perpendicular to the femoral axis.