The calcar femorale redefined.

The calcar femorale is a spur of thickened bone that lies deep to the lesser trochanter but posterior to the neutral axis of the femoral neck. The calcar is thickest medially where it joins the compression buttress of the neck and gradually thins as it passes laterally. X-ray films taken at right angles to the neutral axis of the femoral neck best portray the calcar femorale, which stands out like a solid bone spur as if viewing along the line of a picket fence. The presence of the calcar femorale affects the configuration of peritrochanteric fractures. It should not be confused with the primary medial compression buttress of the femoral neck.