Study on the mechanical properties of tibial cartilage and subchondral bone

软骨下皮层位于钙化软骨薄层的正下方。它是一层致密、坚硬的皮质骨。在成熟的人体中，它形成一个封闭的帽状结构，一边支撑软骨，另一边由松质骨支撑。关于原发性骨关节炎的病因尚未解决的问题，以及最近在膝关节研究中使用有限元分析的兴趣，表明需要关于软骨下骨作为特定结构实体的力学特性的详细数据。然而，由于缺乏适当的局部弹性性能测量方法，目前对软骨下骨力学性能的研究非常有限。本研究采用扫描声学显微镜（SAM）、外周定量计算机断层扫描（pQCT）和压痕法测量了膝关节骨性关节炎患者胫骨近端软骨下骨和关节软骨的弹性模量。胫骨近端钢板取自骨关节病患者胫骨。圆盘状的标本从这些板上的标准化位置用岩心钻加工。标本轴线平行于胫骨长轴。用针刺法测定软骨厚度分布。下面是通过该实验得到的一个实例结果。内髁中央至后部软骨严重损伤，软骨下骨暴露。内侧髁后区软骨下骨的密度和弹性模量均高于前区。

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.