Department of Clinical Neurophysiology, Kuopio University Hospital, P. O. Box 1777, Kuopio 70211, Finland.
Biomech Model Mechanobiol. 2010 Apr;9(2):237-45. doi: 10.1007/s10237-009-0169-y. Epub 2009 Aug 13.
Mechanical function of articular cartilage in joints between articulating bones is dependent on the composition and structure of the tissue. The mechanical properties of articular cartilage are traditionally tested in compression using one of the three loading geometries, i.e., confined compression, unconfined compression or indentation. The aim of this study was to utilize a composition-based finite element model in combination with a fractional factorial design to determine the importance of different cartilage constituents in the mechanical response of the tissue, and to compare the importance of the tissue constituents with different loading geometries and loading rates. The evaluated parameters included water and collagen fraction as well as fixed charge density on cartilage surface and their slope over the tissue thickness. The thicknesses of superficial and middle zones, as based on the collagen orientation, were also included in the evaluated parameters. A three-level resolution V fractional factorial design was used. The model results showed that inhomogeneous composition plays only a minor role in indentation, though that role becomes more significant in confined compression and unconfined compression. In contrast, the collagen architecture and content had a more profound role in indentation than with two other loading geometries. These differences in the mechanical role of composition and structure between the loading geometries were emphasized at higher loading rates. These findings highlight how the results from mechanical tests of articular cartilage under different loading conditions are dependent upon tissue composition and structure.
关节软骨在关节骨之间的机械功能取决于组织的组成和结构。关节软骨的机械性能传统上采用三种加载几何形状之一进行压缩测试，即约束压缩、无约束压缩或压痕。本研究旨在利用基于成分的有限元模型结合分数阶因子设计来确定不同软骨成分在组织力学响应中的重要性，并比较组织成分在不同加载几何形状和加载速率下的重要性。评估的参数包括水和胶原分数以及软骨表面的固定电荷密度及其在组织厚度上的斜率。根据胶原取向评估的参数还包括浅层和中层的厚度。使用了三级分辨率 V 分数阶因子设计。模型结果表明，不均匀的组成在压痕中只起次要作用，尽管在约束压缩和无约束压缩中作用更为显著。相比之下，胶原结构和含量在压痕中的作用比另外两种加载几何形状更为深远。在较高的加载速率下，这些加载几何形状之间在组成和结构的机械作用上的差异更为明显。这些发现强调了在不同加载条件下对关节软骨进行机械测试的结果如何取决于组织的组成和结构。
