Jurvelin J S, Buschmann M D, Hunziker E B
M. E. Müller Institute for Biomechanics, University of Bern, Switzerland.
J Biomech. 1997 Mar;30(3):235-41. doi: 10.1016/s0021-9290(96)00133-9.
The equilibrium stiffness of articular cartilage is controlled by flow-independent elastic properties (Young's modulus, ES, and Poisson's ratio, v(s)) of the hydrated tissue matrix. In the current study, an optical (microscopic) method has been developed for the visualization of boundaries of cylindrical bovine humeral head articular cartilage disks (n = 9), immersed in physiological solution, and compressed in unconfined geometry. This method allowed a direct, model-independent estimation of Poisson's ratio of the tissue at equilibrium, as well as characterization of the shape changes of the sample during the nonequilibrium dynamic phase. In addition to optical analyses, the equilibrium behavior of cartilage disks in unconfined and confined ramp-stress relaxation tests provided a direct estimation of the aggregate modulus, H(a) and Young's modulus and, indirectly, Poisson's ratio for the articular cartilage. The mean value for Poisson's ratio obtained from the optical analysis was 0.185 +/- 0.065 (mean +/- S.D., n = 9). Values of elastic parameters obtained from the mechanical tests were 0.754 +/- 0.198 MPa, 0.677 +/- 0.223 MPa, and 0.174 +/- 0.106 for H(a), ES, and v(s), respectively (mean +/- S.D., n = 7). The similar v(s)-values obtained with optical and mechanical techniques imply that, at equilibrium for these two tests, the isotropic model is acceptable for mechanical analysis. However, the microscopic technique revealed that the lateral expansion, especially during the initial phase of relaxation, was inhomogeneous through the tissue depth. The superficial cartilage zone expanded less than the radial zone. The zonal differences in expansion were attributed to the known zonal differences in the fibrillar collagen architecture and proteoglycan concentration.
关节软骨的平衡刚度由水合组织基质的与流动无关的弹性特性（杨氏模量、弹性储能模量和泊松比ν(s)）控制。在本研究中，已开发出一种光学（显微镜）方法，用于观察浸泡在生理溶液中并在无侧限几何形状下受压的圆柱形牛肱骨头关节软骨盘（n = 9）的边界。该方法允许直接、独立于模型地估计组织在平衡时的泊松比，以及表征样品在非平衡动态阶段的形状变化。除了光学分析外，在无侧限和有侧限的斜坡应力松弛试验中软骨盘的平衡行为还提供了对聚集模量H(a)、杨氏模量的直接估计，并间接得出关节软骨的泊松比。通过光学分析获得的泊松比平均值为0.185±0.065（平均值±标准差，n = 9）。从力学试验获得的弹性参数值，H(a)、弹性储能模量和ν(s)分别为0.754±0.198 MPa、0.677±0.223 MPa和0.174±0.106（平均值±标准差，n = 7）。通过光学和力学技术获得的相似ν(s)值表明，对于这两种试验在平衡时，各向同性模型对于力学分析是可接受的。然而，显微镜技术显示，横向膨胀，尤其是在松弛的初始阶段，在组织深度上是不均匀的。表层软骨区的膨胀小于径向区。膨胀的区域差异归因于原纤维胶原结构和蛋白聚糖浓度中已知的区域差异。
