van der Veen Albert J, Mullender Margriet G, Kingma Idsart, van Dieen Jaap H, Smit Theo H
Department of Physics and Medical Technology, VU University Medical Center, Research Institute MOVE, De Boelelaan 1117, 1081HV Amsterdam, The Netherlands.
J Biomech. 2008;41(6):1260-8. doi: 10.1016/j.jbiomech.2008.01.010. Epub 2008 Mar 6.
Spinal segments show non-linear behavior under axial compression. It is unclear to what extent this behavior is attributable to the different components of the segment. In this study, we quantified the separate contributions of vertebral bodies and intervertebral discs to creep of a segment. Secondly, we investigated the contribution of bone and osteochondral endplate (endplates including cartilage) to the deformation of the vertebral body. From eight porcine spines a motion segment, a disc and a vertebral body were dissected and subjected to mechanical testing. In an additional test, cylindrical samples, machined from the lowest thoracic vertebrae of 11 porcine spines, were used to compare the deformation of vertebral bone and endplate. All specimens were subjected to three loading cycles, each comprising a loading phase (2.0 MPa, 15 min) and a recovery phase (0.001 MPa, 30 min). All specimens displayed substantial time-dependent height changes. Average creep was the largest in motion segments and smallest in vertebral bodies. Bone samples with endplates displayed substantially more creep than samples without. In the early phase, behavior of the vertebra was similar to that of the disc. Visco-elastic deformation of the endplate therefore appeared dominant. In the late creep phase, behavior of the segment was similar to that of isolated discs, suggesting that in this phase the disc dominated creep behavior, possibly by fluid flow from the nucleus. We conclude that creep deformation of vertebral bodies contributes substantially to creep of motion segments and that within a vertebral body endplates play a major role.
脊柱节段在轴向压缩下呈现非线性行为。目前尚不清楚这种行为在多大程度上可归因于节段的不同组成部分。在本研究中，我们量化了椎体和椎间盘对节段蠕变的单独贡献。其次，我们研究了骨和骨软骨终板（包括软骨的终板）对椎体变形的贡献。从8个猪脊柱中解剖出一个运动节段、一个椎间盘和一个椎体，并进行力学测试。在另一项测试中，使用从11个猪脊柱的最低胸椎加工而成的圆柱形样本，比较椎体骨和终板的变形。所有标本均经历三个加载循环，每个循环包括一个加载阶段（2.0MPa，15分钟）和一个恢复阶段（0.001MPa，30分钟）。所有标本均显示出显著的时间依赖性高度变化。平均蠕变在运动节段中最大，在椎体中最小。带有终板的骨样本显示出比没有终板的样本更多的蠕变。在早期阶段，椎体的行为与椎间盘相似。因此，终板的粘弹性变形似乎占主导地位。在后期蠕变阶段，节段的行为与孤立椎间盘相似，这表明在这个阶段，椎间盘主导蠕变行为，可能是由于髓核中的流体流动。我们得出结论，椎体的蠕变变形对运动节段的蠕变有很大贡献，并且在椎体内终板起主要作用。
