Iatridis J C, Setton L A, Weidenbaum M, Mow V C
Department of Orthopaedics and Rehabilitation, University of Vermont, Burlington 05405-0084, USA.
J Orthop Res. 1997 Mar;15(2):318-22. doi: 10.1002/jor.1100150224.
This study tested the hypothesis that changes in the morphology and composition of the nucleus pulposus with age and degeneration have associated changes in its mechanical properties. A torsional shear experiment was used to determine viscoelastic shear properties of cylindrical samples of human nucleus pulposus with large ranges of grades of morphological degeneration (normal to severely degenerated) and ages (range: 16-88 years; average: 57 +/- 21.5 years). Viscoelastic shear properties were determined from stress-relaxation and dynamic sinusoidal tests. A linear viscoelastic law with a variable-amplitude relaxation spectrum was used to model experimental behaviors of nucleus pulposus specimens. A statistically significant increase in the instantaneous and dynamic shear moduli was found with increasing age and grade of degeneration; the values for moduli ranged from 5.0 to 60 kPa. A significant decrease in tan delta was also detected; the values ranged from 0.43 to 0.33, indicating a decreased capacity for the nucleus pulposus to dissipate energy. The dynamic modulus and tan delta were also significantly affected by frequency. It was generally concluded that the nucleus pulposus undergoes a transition from "fluid-like" behavior to more "solid-like" behavior with aging and degeneration.
随着年龄增长和椎间盘退变，髓核的形态和组成变化会使其力学性能发生相应改变。采用扭转剪切试验来测定形态退变程度（从正常到严重退变）和年龄范围较大（16 - 88岁；平均年龄：57 ± 21.5岁）的人髓核圆柱形样本的粘弹性剪切特性。通过应力松弛和动态正弦试验确定粘弹性剪切特性。使用具有可变振幅松弛谱的线性粘弹性定律对髓核样本的实验行为进行建模。结果发现，随着年龄增长和退变程度加重，瞬时剪切模量和动态剪切模量在统计学上显著增加；模量值范围为5.0至60 kPa。还检测到损耗因子（tanδ）显著降低；其值范围为0.43至0.33，表明髓核耗散能量的能力下降。动态模量和损耗因子也受频率的显著影响。总体结论是，随着衰老和退变，髓核经历了从“类流体”行为到更“类固体”行为的转变。
