Nonlinear tensile properties of bovine articular cartilage and their variation with age and depth
Nonlinear tensile properties of bovine articular cartilage and their variation with age and depth
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DOI：
10.1115/1.1688771
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发表时间：
2004-04-01
影响因子：
1.7
通讯作者：
Buschmann, MD
中科院分区：
文献类型：
--
作者：
Charlebois, M;McKee, MD;Buschmann, MD
关节软骨的拉伸刚度远大于其压缩刚度，并且通过在生理负荷期间增加瞬态流体压力而在压缩特性中起重要作用。最近的非线性特性的关节软骨在压缩的研究揭示了几个生理相关的非线性行为，所有这些都需要软骨拉伸刚度显着增加拉伸。因此，我们进行了一系列的单轴拉伸试验新鲜牛关节软骨切片使用的协议，允许几个小时达到平衡，并测量纵向和横向组织应变。通过测试不同年龄（6个月至6岁）的牛软骨，我们发现，平衡和瞬态拉伸模量随成熟和年龄显着增加，从0到15 MPa的平衡和从10到28 MPa的瞬态。我们的研究结果表明，软骨随着年龄的增长，以类似于其他高度水合的结缔组织的方式变硬，可能是由于酶和非酶胶原交联的年龄依赖性含量。在我们的测试中使用的长松弛时间（5-10小时）是必要的，以便达到平衡，并避免当使用短得多的时间（15-30分钟）时发生的非常显著的平衡模量高估。我们还发现，当软骨从0拉伸到10%应变时，平衡和瞬态拉伸模量非线性增加，而没有任何先前的拉伸载荷。虽然我们的研究结果估计拉伸刚度的非线性增加与拉伸，这是一个数量级低于所需的预测压缩非线性特性，他们与以前的结果从其他单轴拉伸试验的胶原材料。因此，我们推测，双轴拉伸模量可能更高，从而更符合观察到的非线性压缩性能。
Tensile stiffness of articular cartilage is much greater than its compressive stiffness and plays an essential role even in compressive properties by increasing transient fluid pressures during physiological loading. Recent studies of nonlinear properties of articular cartilage in compression revealed several physiologically pertinent nonlinear behaviors, all of which required that cartilage tensile stiffness increase significantly with stretch. We therefore performed sequences of uniaxial tension tests on fresh bovine articular cartilage slices using a protocol that allowed several hours to attain equilibrium and measured longitudinal and transverse tissue strain. By testing bovine cartilage from different ages (6 months to 6 years) we found that equilibrium and transient tensile modulus increased significantly with maturation and age, from 0 to 15 MPa at equilibrium and from 10 to 28 MPa transiently. Our results indicate that cartilage stiffens with age in a manner similar to other highly hydrated connective tissues, possibly due to age-dependent content Of enzymatic and nonenzymatic collagen cross links. The long relaxation period used in our tests (5-10 hours) was necessary in order to attain equilibrium and avoid a very significant overestimation of equilibrium modulus that occurs when much shorter times are used (15-30 minutes). We also found that equilibrium and transient tensile modulus increased nonlinearly when cartilage is stretched from 0 to 10% strain without any previous tare load. Although our results estimate a nonlinear increase in tensile stiffness with stretch that is an order of magnitude lower than that required to predict nonlinear properties in compression, they are in agreement with previous results from other uniaxial tension tests of collagenous materials. We therefore speculate that biaxial tensile moduli may be much higher and thereby more compatible with observed nonlinear compressive properties.