Pollintine P, Przybyla A S, Dolan P, Adams M A
Department of Anatomy, University of Bristol, Bristol BS2 8EJ, UK.
J Biomech. 2004 Feb;37(2):197-204. doi: 10.1016/s0021-9290(03)00308-7.
We validate a technique for measuring neural arch load-bearing in cadaveric spines, and use it to test the hypothesis that such load-bearing rises to high levels in old and degenerated spines. Fifty-nine cadaveric lumbar motion segments, aged 19-92 yr, were subjected to compressive creep loading to reduce intervertebral disc water content and height to in vivo levels. The distribution of compressive "stress" within the disc was then measured by pulling a miniature pressure transducer, side-mounted in a 1.3mm-diameter needle, along its mid-sagittal diameter. During these measurements, the motion segment was subjected to a compressive load of 2 kN, and positioned in 2 degrees of extension to simulate erect standing. Measurements of compressive "stress" were integrated over disc area, and this force subtracted from the applied 2 kN to give the force resisted by the neural arch. An empirical calibration factor was applied to normalise results from each disc to values obtained under conditions when all of the compressive force could be assumed to pass through the disc. Disc degeneration was graded macroscopically on a scale of 1-4. Validation tests showed that calculated values of disc loading were proportional to actual applied load (r(2)>0.96) and predicted it with errors of 2-8%. Neural arch load-bearing in non-degenerated specimens was generally less than 20%, but averaged 49% for specimens aged over 70 yr. Multiple regression showed that neural arch load bearing (%)=14.4 x disc degeneration score+0.46 x age-35. These results indicate a substantial shift in vertebral load-bearing with increasing age and degeneration.
我们验证了一种测量尸体脊柱神经弓承重的技术，并使用该技术来检验这样一个假设：在老化和退变的脊柱中，这种承重会升高到很高水平。59个年龄在19 - 92岁之间的尸体腰椎运动节段，接受压缩蠕变加载，以将椎间盘含水量和高度降低到体内水平。然后，通过沿着其矢状中径拉动一个侧面安装在直径1.3毫米针内的微型压力传感器，来测量椎间盘内的压缩“应力”分布。在这些测量过程中，运动节段承受2 kN的压缩载荷，并处于2度伸展位以模拟直立站立。将压缩“应力”测量值在椎间盘面积上进行积分，并从施加的2 kN中减去该力，以得到神经弓抵抗的力。应用一个经验校准因子，将每个椎间盘的结果归一化为在所有压缩力都可假定通过椎间盘的条件下获得的值。椎间盘退变通过肉眼在1 - 4级的范围内进行分级。验证测试表明，计算得到的椎间盘负荷值与实际施加的负荷成正比（r(2)>0.96），预测误差为2 - 8%。未退变标本的神经弓承重一般小于20%，但70岁以上标本的平均值为49%。多元回归显示，神经弓承重（%）=14.4×椎间盘退变评分 + 0.46×年龄 - 35。这些结果表明，随着年龄增长和退变，椎体承重发生了显著变化。
