Fluid pressure driven fibril reinforcement in creep and relaxation tests of articular cartilage
Fluid pressure driven fibril reinforcement in creep and relaxation tests of articular cartilage
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DOI：
10.1016/j.medengphy.2007.03.001
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发表时间：
2008-03-01
影响因子：
2.2
通讯作者：
Herzog, W.
中科院分区：
文献类型：
--
作者：
Li, L. P.;Korhonen, R. K.;Herzog, W.
生物组织具有复杂的材料特性，表现出不同的力学行为。正如韧带和椎间盘所显示的那样，通过调整模型参数，数学模型往往似乎能够很好地单独预测载荷响应，但很可能无法使用相同的模型参数同时描述几种不同的载荷响应。在本研究中，我们尝试使用纤维增强模型来描述和解释关节软骨的蠕变和松弛响应，该模型已成功地用于解释关节软骨松弛试验的载荷响应。实验在牛关节软骨盘(n=8)上进行，采用多步加载方案，每个方案都包括蠕变和松弛。实验结果表明，在拉伸过程中，纤维在胶原网络中的聚集等力学变化在卸载后完全恢复。蠕变加载不影响松弛性能，反之亦然。由于流体压力分布的不同，松弛比蠕变进行得快得多。对于蠕变和松弛测试，蛋白多糖基质、胶原网络和流体加压之间的负荷分担被预测为不同的。如果忽略纤维增强或流体加压，则无法预测在无侧限压缩下实验观察到的强烈蠕变和松弛响应。考虑到非线性纤维增强和流体加压之间的相互作用对于瞬时响应是至关重要的(这种相互作用最好被称为流体压力驱动的纤维增强)。在平衡状态下，纤维强化在压缩载荷响应中的作用相对较小，这与先前的软骨应力松弛测试结果一致。(C)2007年IPEM。爱思唯尔有限公司出版。保留所有权利。
Biological tissues exhibit diverse mechanical behaviors because of complex material properties. As has been shown for ligaments and intervertebral discs, mathematical models often appear to well predict load responses individually by adjusting model parameters, but likely fail to describe several different load responses simultaneously using the same model parameters. In the present study, we attempted to describe and explain both creep and relaxation responses of articular cartilage using a fibril-reinforced model, which has been successfully used to account for the load response of the relaxation tests of articular cartilage. Experiments were performed on bovine articular cartilage disks (n = 8) using multi-step loading protocols, involving both creep and relaxation in each protocol. The experimental results indicated that mechanical changes, such as fiber recruitment in collagen network during stretch, recovered fully upon unloading. Creep loading did not affect relaxation properties, and vice versa. Relaxation proceeded much faster than creep, because of different fluid pressure profiles. The load sharing among the proteoglycan matrix, collagen network and fluid pressurization was predicted to differ for the creep and relaxation testing. The experimentally observed strong creep and relaxation responses in unconfined compression could not be predicted if either fibril reinforcement or fluid pressurization were neglected. It was essential to consider the interplay between nonlinear fibril reinforcement and fluid pressurization for the transient response (this interplay may be best termed as fluid pressure driven fibril reinforcement). Fibril reinforcement played a relatively insignificant role in the compressive load response at equilibrium, in agreement with previous findings for cartilage stress relaxation testing. (c) 2007 IPEM. Published by Elsevier Ltd. All rights reserved.