Fig. 2
From: Three-dimensional morphological analysis of the femoral neck torsion angle—an anatomical study
The method for determining the coronal plane and axis of the proximal femur.
The blue line through points A and B (the centers of the inner connecting circles of these two cross-sections represent 25% and 35% of the length of the femur shaft) was defined as the axis of the proximal femur. The gray plane perpendicular to the coronal plane (yellow) of the femur through points A and B was defined as plane A, and then a plane perpendicular to plane A was defined as plane B (red), which was also designated the coronal plane of the proximal femur