MATERIAL PROPERTIES OF BONE FROM THE FEMORAL-NECK AND CALCAR FEMORALEOF PATIENTS WITH OSTEOPOROSIS OR OSTEOARTHRITIS

Patients with osteoarthritis (OA) rarely fracture the neck of the femu r whereas this is common in patients with osteoporosis (OP). The reaso ns for this are not clear. In this study, cores of trabecular bone and thin slices of bone from the calcar were obtained from the femoral ne ck of patients with OA or OP following hip arthroplasty and a normal g roup post mortem. The mechanical properties, densities and material co mposition were measured. The aim was to determine whether differences in these properties could explain why osteoarthritic patients did not suffer from fractured neck of femur. No difference was found in the de nsity or stiffness of the calcar between the groups, though there appe ared to be a small increase in mineralization in the OA bone compared with the OF. However, there was a 72% increase in the volume of trabec ular bone in the OA group compared with a loss of about 20% in the OP group. This increased apparent density of the OA trabecular bone resul ted in a greater stiffness, yield strength and energy absorbed to yiel d, whereas the same properties of OP bone were not significantly lower than normal. These marked changes in the OA bone could result in a re distribution of stresses due to loads caused by falling, thereby absor bing the energy of impact and preventing the formation of a fracture s urface.