MECHANICAL AND MATERIAL PROPERTIES OF THE SUBCHONDRAL BONE PLATE FROMTHE FEMORAL-HEAD OF PATIENTS WITH OSTEOARTHRITIS OR OSTEOPOROSIS

Objective-To determine the material properties of the subchondral bone plate in patients with osteoarthritis or osteoporosis. Methods-Femora l heads were obtained after surgical removal from age and sex matched groups of patients with either osteoporosis (OF), after a fractured ne ck of femur, or osteoarthritis (OA) and compared with a normal group. The mechanical stiffness, density, and composition of the subchondral bone plate from sites selected to represent areas of heavy, intermitte nt, and light loading were measured. Results-Overall, OP bone was the least stiff and dense, followed by OA bone; normal bone was stiffer an d more dense (p < 0.05). Though OP bone contained less mineral, the or ganic and water contents were increased in proportion suggesting no ch ange in the relative amount of organic matrix. OA bone was also hypomi neralised (p < 0.05) but had different organic and water fractions sug gesting a defect in the matrix. Site variation of most properties was small, though across all the groups the superior region was significan tly stiffer than the inferior. Conclusion-This study shows that subcho ndral bone plate is less stiff than normal in both OP and OA and so ca nnot, by itself, explain the preserving of the overlying cartilage in OP while aiding its destruction in OA. However, the subchondral bone p late is only one part of the bony structure of the femoral head and ch anges in the cancellous bone need to be considered. The generalised ch anges in bone composition found in patients with OA support the hypoth esis that the disease could involve the bone in the primary pathogenes is.