Li L P, Soulhat J, Buschmann M D, Shirazi-Adl A
Departments of Chemical Engineering, Institute of Biomedical Engineering, Ecole Polytechnique of Montreal, P.O. Box 6079, Station Centre-ville, Montreal, Quebec, Canada.
Clin Biomech (Bristol). 1999 Nov;14(9):673-82. doi: 10.1016/s0268-0033(99)00013-3.
To develop a biomechanical model for cartilage which is capable of capturing experimentally observed nonlinear behaviours of cartilage and to investigate effects of collagen fibril reinforcement in cartilage.
A sequence of 10 or 20 steps of ramp compression/relaxation applied to cartilage disks in uniaxial unconfined geometry is simulated for comparison with experimental data.
Mechanical behaviours of cartilage, such as the compression-offset dependent stiffening of the transient response and the strong relaxation component, have been previously difficult to describe using the biphasic model in unconfined compression.
Cartilage is modelled as a fluid-saturated solid reinforced by an elastic fibrillar network. The latter, mainly representing collagen fibrils, is considered as a distinct constituent embedded in a biphasic component made up mainly of proteoglycan macromolecules and a fluid carrying mobile ions. The Young's modulus of the fibrillar network is taken to vary linearly with its tensile strain but to be zero for compression. Numerical computations are carried out using a finite element procedure, for which the fibrillar network is discretized into a system of spring elements.
The nonlinear fibril reinforced poroelastic model is capable of describing the strong relaxation behaviour and compression-offset dependent stiffening of cartilage in unconfined compression. Computational results are also presented to demonstrate unique features of the model, e.g. the matrix stress in the radial direction is changed from tensile to compressive due to presence of distinct fibrils in the model.
Experimentally observed nonlinear behaviours of cartilage are successfully simulated, and the roles of collagen fibrils are distinguished by using the proposed model. Thus this study may lead to a better understanding of physiological responses of individual constituents of cartilage to external loads, and of the roles of mechanical loading in cartilage remodelling and pathology.
建立一个能够捕捉实验观察到的软骨非线性行为的软骨生物力学模型，并研究胶原纤维增强在软骨中的作用。
模拟在单轴无侧限几何形状下对软骨盘施加10或20步斜坡压缩/松弛序列，以与实验数据进行比较。
软骨的力学行为，如瞬态响应的压缩偏移依赖性硬化和强烈的松弛成分，以前在无侧限压缩中使用双相模型很难描述。
将软骨建模为一种由弹性纤维网络增强的流体饱和固体。后者主要代表胶原纤维，被视为嵌入主要由蛋白聚糖大分子和携带移动离子的流体组成的双相成分中的一种独特成分。纤维网络的杨氏模量被认为随其拉伸应变线性变化，但在压缩时为零。使用有限元程序进行数值计算，其中纤维网络被离散化为弹簧单元系统。
非线性纤维增强多孔弹性模型能够描述软骨在无侧限压缩中的强烈松弛行为和压缩偏移依赖性硬化。还给出了计算结果以展示该模型的独特特征，例如由于模型中存在不同的纤维，径向方向的基质应力从拉伸变为压缩。
成功模拟了实验观察到的软骨非线性行为，并通过所提出的模型区分了胶原纤维的作用。因此，本研究可能有助于更好地理解软骨单个成分对外部载荷的生理反应，以及机械载荷在软骨重塑和病理学中的作用。
