van Deursen D L, Snijders C J, Kingma I, van Dieën J H
Department of Biomedical Physics and Technology, Erasmus University, Rotterdam, The Netherlands.
Spine (Phila Pa 1976). 2001 Dec 1;26(23):2582-6. doi: 10.1097/00007632-200112010-00011.
A cadaveric porcine spine motion segment experiment was conducted.
To test the hypothesis that small vertebral rotations cause increased stress in the anulus while decreasing stress in the nucleus through stiffening of the anulus.
Stress profiles of the intervertebral disc reportedly depend on degeneration grade and external loading. Increased stress in the anulus was found during asymmetric loading. In addition, depressurization of the nucleus combined with an instantaneous disc height increase was found when small (<2 degrees ) axial vertebral rotations were applied.
Seven lumbar porcine cadaveric motion segments consisting of two vertebrae and the intervening disc with ligaments were loaded in the neutral position with 340 N of compression. Stress profiles were obtained in the neutral position, then after 0.5 degrees and 1 degrees axial rotation of the bottom vertebral body. The distribution of compressive stress in the disc matrix was measured by pulling a miniature pressure transducer through the disc along a straight path in the midfrontal plane. Stress profiles were measured in vertical (0 degrees ) and horizontal (90 degrees ) orientation.
Deformation of the anulus by small axial rotations of the lower vertebra instantaneously decreased the horizontally and vertically measured stress in the nucleus while increasing stress in the anulus. A 1-hour period of creep loading decreased the stresses in the nucleus and the anulus 20% to 30%, depending on the orientation, but the effect of an increasing stress in the anular region after axial rotation persisted.
The compressive Young's modulus of the composite anulus tissue increases instantaneously when small axial rotations are applied to porcine spine motion segments. This is accompanied by decreased stress in the nucleus pulposus, increased stress in the anulus fibrosus, changes in the stress profile superimposed on and independent of prolonged viscoelastic creep and dehydration, and changes in stress distribution independent of horizontal and vertical orientation.
进行了一项猪尸体脊柱运动节段实验。
检验以下假设，即小幅度椎体旋转会通过使纤维环变硬而增加纤维环应力，同时降低髓核应力。
据报道，椎间盘的应力分布取决于退变程度和外部负荷。在不对称负荷期间发现纤维环应力增加。此外，当施加小幅度（<2度）轴向椎体旋转时，发现髓核减压并伴有椎间盘高度瞬间增加。
对7个包含两个椎体以及其间带韧带椎间盘的猪腰椎尸体运动节段在中立位施加340N的压缩负荷。在中立位获取应力分布，然后在底部椎体进行0.5度和1度轴向旋转后再次获取。通过将微型压力传感器沿额状面中线的直线路径拉过椎间盘来测量椎间盘基质中的压应力分布。在垂直（0度）和水平（90度）方向测量应力分布。
下部椎体的小幅度轴向旋转使纤维环变形，瞬间降低了在水平和垂直方向测量的髓核应力，同时增加了纤维环应力。1小时的蠕变负荷使髓核和纤维环应力降低20%至30%，具体取决于方向，但轴向旋转后纤维环区域应力增加的效应仍然存在。
对猪脊柱运动节段施加小幅度轴向旋转时，复合纤维环组织的压缩杨氏模量会瞬间增加。这伴随着髓核应力降低、纤维环应力增加、叠加于并独立于长期粘弹性蠕变和脱水的应力分布变化，以及与水平和垂直方向无关的应力分布变化。
