Chemical composition of normal and osteoarthrotic cancellous bone of the femoral head. Studies of EDTA extracts and collagenase digests.

Using EDTA extraction and collagenase digestion, cancellous bone from the femoral heads of ten normal and eight osteoarthrotic individuals was analyzed for its content of collagen, sialoprotein, proteoglycan, and carbohydrate. The EDTA extractability of the matrix proteins of the osteoarthrotic bone was significantly increased (P less than 0.001), as was the soluble collagenase-resistant fraction (SCRF). EDTA residues, bone matrix size, the collagenase-resistant fraction (CRF), and the insoluble collagenase-resistant fraction (ICRF) of the osteoarthrotic cases were not different from those of the controls. The amounts of carbohydrate and proteoglycans were considerably elevated in the bone matrix of the osteoarthrotic bone (P less than 0.01 and P less than 0.001, respectively). In the EDTA extracts, sialoprotein and proteoglycan contents were found in significant higher amounts (P less than 0.05 and P less than 0.01, respectively) in the osteoarthrotic cases. In the SCRF, the hexose and sialic acid contents were higher in the osteoarthrotic bone (P less than 0.01), while in the ICRF all the analyses were significantly increased in the osteoarthrotic bone (P less than 0.001). The ratios of collagen to non-collagenous components were lower in the osteoarthrotic than in normal bones. The quantitative and qualitative variations in cancellous bone proteins from the femoral head in osteoarthrosis found in this study suggest that alterations in subchondral bone play a role in the pathophysiology of cartilage degeneration in osteoarthrosis.