Regional variation of bone matrix components in osteoarthrotic and normal femoral heads.

Three regios of cancellous bone, two subchondral and one central, from the femoral heads of five normal and ten osteoarthrotic individuals were analysed for their content of collagen, sialoprotein, proteoglycan and carbohydrate. Confirming previous findings in osteoarthrotic bone this study shows that there are significant quantitative changes in matrix composition consisting of a decrease in collagen content and increase in noncollagenous proteins in osteoarthrosis. Since these matrix alterations were present in all areas of the femoral head, also at areas distal from the subchondral area, it is unlikely that these changes are secondary to bone remodeling near the joint destruction. Difference in matrix composition according to the area of the femoral head was also found in the controls, indicating that bone matrix proteins are related to mechanic properties of the bone. The more stress the bone has to withstand, the lower the collagen/noncollagenous protein ratio in its matrix. These observations suggest that in osteoarthrosis, the bone is stiffer and can therefore absorb less well impact loading and by transmitting it back to the cartilage provokes cartilage dysfunction.