A comparison of the stiffness, density and composition of bone from the calcar femorale and the femoral cortex.

The stiffness, density and composition were compared in bone from the calcar femorale and cortical bone from the mid-shaft of the femur from an elderly group of clinically normal patients. Variation of properties through the thickness of the bone and the stiffness, measured using ultrasound, in directions parallel and perpendicular to the bone axis were also investigated. The calcar was less stiff (30.5 GPa) than the cortical bone (33.0 GPa) (P=0.04). It was also slightly less dense (2.01 compared with 2.05 g cm-3, P<0.001)and had a lower mineral content (56.7% of wet mass) than the femoral cortex (58.0%, P<0.05). At both sites the bone stiffness, density and mineral content decreased from the outer layer towards the inside. The stiffness was greatest in an axial direction and least in a radial direction with the tangential stiffness slightly greater than the radial, indicating an orthotropic symmetry. These results show that bone from the calcar has similar material properties to cortical bone, and provide a baseline for further studies investigating possible changes in the calcar in osteoporosis which may increase our understanding of the mechanisms underlying fractures of the neck of the femur. Copyright 1998 Kluwer Academic Publishers