Is the nucleus pulposus a solid or a fluid? Mechanical behaviors of the nucleus pulposus of the human intervertebral disc
Is the nucleus pulposus a solid or a fluid? Mechanical behaviors of the nucleus pulposus of the human intervertebral disc
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DOI：
10.1097/00007632-199605150-00009
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发表时间：
1996-05-15
期刊：
影响因子：
3
通讯作者：
Mow, VC
中科院分区：
文献类型：
--
作者：
Iatridis, JC;Weidenbaum, M;Mow, VC
研究设计.本研究采用一种新的技术测量髓核在剪切力作用下的粘弹性行为，以评估其固体和流体特性。回顾现有的髓核力学行为的知识，并开发一种新的技术来研究在瞬态和动态条件下的扭转（纯）剪切的孤立髓核样本的粘弹性行为。我进行了大量的研究，研究了核的膨胀行为，发现膨胀压力的范围约为0.05-3 MPa，这取决于加载条件。然而，很少有研究探讨髓核的负荷变形行为。从腰椎间盘采集13个非退化髓核样本，并在瞬态和动态测试条件下进行扭转剪切测试。采用具有变幅松弛谱的线性粘弹性规律模拟应力松弛和动态频率扫描实验。粘弹性定律的系数由应力松弛实验确定，而动态剪切模量和相移角由频率扫描确定。核在剪切中表现出显著的粘弹性效应。在瞬态条件下，应力松弛到接近零的值，这表明原子核的“类流体”行为。然而，在动态条件下，核的材料参数，复模量的大小（7-21千帕），和相位角（23-31度）的粘弹性固体的更多的特征。作者提出的应力-应变规律与粘弹性数据吻合良好。在剪切变形的反应，髓核表现出显着的粘弹性效应，流体和固体的特性。髓核在体内表现为流体还是固体取决于加载速率。
Study Design. A new technique to measure the viscoelastic behavior of the nucleus pulposus in shear was used to assess its solid and fluid characteristics.Objectives. To review existing knowledge on mechanical behaviors of the nucleus pulposus,and to develop a new technique to study the viscoelastic behaviors of isolated nucleus pulposus samples in torsional (pure) shear under transient and dynamic conditions.Summary of Background Data. Numerous studies I have investigated the swelling behavior of the nucleus and found the swelling pressure to range approximately 0.05-3 MPa, depending on loading conditions. Very few studies, however, have investigated the loading deformational behaviors of the nucleus pulposus.Methods. Thirteen nondegenerate samples of nucleus pulposus were harvested from lumbar discs and tested in torsional shear under transient and dynamic test conditions. A linear viscoelastic law with variable amplitude relaxation spectrum was used to model the stress relaxation and dynamic frequency sweep experiments. The coefficients of the viscoelastic law were determined from the stress relaxation experiments, whereas the dynamic shear modulus and phase shift angle were determined from the frequency sweep.Results. The nucleus exhibits significant viscoelastic effects in shear. Under transient conditions, the stress relaxed to values near zero, which is indicative of the ''fluid-like'' behaviors of the nucleus. Under dynamic conditions, however, the material parameters for the nucleus, magnitude of the complex modulus (7-21 kPa), and phase angle (23-31 degrees) were more characteristic of a viscoelastic solid. The authors' proposed stress-strain law exhibited excellent agreement with the viscoelastic data.Conclusions. In response to shear deformations, the nucleus pulposus exhibited significant viscoelastic effects, characteristic of a fluid and a solid. Whether the nucleus pulposus behaves more as a fluid or a solid in vivo depends on the rate of loading.