Triangular structure of the proximal femur.

The normal human skeleton is remarkably regular in form. Its constancy is demonstrated by the projection of well-recognized lines onto plain radiographs to define many of its relationships. The finding of the geometric symmetry of the normal proximal femur, demonstrated by the projection of an isosceles triangle onto its anteroposterior radiographic view, is presented. The base of this triangle extends between the trochanters and its apex lies at the center of the femoral head. This triangle may reflect the balance of bone modeling that takes place in the proximal femur as a result of the forces acting in the coronal plane. If so, it may then allow for the development of a mathematical expression for bone modeling in this plane. Copyright 2002 Wiley-Liss, Inc.