Study on the mechanical properties of tibial cartilage and subchondral bone

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The subchondral cortex lies immediately below the thin layer of calcified cartilage. It is a layer dense, stiff, cortical bone. In the mature human, it forms a closed cap supporting the cartilage on one side and supported by the cancellous bone on the other. Unanswered questions regarding the etiology of primary osteoarthritis, as well as the recent interest in the use of finite element analysis in the study of knee joint, suggest a need for detailed data on the mechanical properties of subchondral bone as a specific structural entity. However, only limited information is presently available on mechanical property of subchondral bone because of the lack of appropriate local elastic property measuring method.In this study we measured the elastic modulus of human proximal tibial subchondral bone and articular cartilage in the osteoarthritis of knee joint using the scanning acoustic microscope (SAM), peripheral quantitative computed tomography (pQCT) and the indentation method. Proximal tibial plates were taken from human tibiae of osteoarthrosis joints. Disc-shaped specimens were machined from standardized locations on these plates with a core drill. The axes of the specimens were parallel to the long axis of tibia. The distribution of cartilage thickness was measured by needle method. Following is an example results obtain through this experiment. There is a serious damage on the cartilage from the center to posterior of medial condyle and the subchondral boneis exposed. In the medial condyle, the density and the elastic modulus of the subchondral bone is higher at posterior area than anterior.