Tyndyk M A, McGarry J P, Barron V, McHugh P E, O'Mahoney D, Tawackoli W, Liebschner M A K
National Centre for Biomedical Engineering Science, National University of Ireland, Galway, Ireland.
J Long Term Eff Med Implants. 2008;18(4):269-88. doi: 10.1615/jlongtermeffmedimplants.v18.i4.20.
The objective of this study was to investigate the effects of intervertebral disk degeneration on the flexibility of the thoracolumbar spine in flexion and extension, both experimentally and computationally. A seven-level biomechanically tested human cadaveric spine (T11-L5) and a 3D finite element model of the same thoracolumbar spine were used for this purpose. The anatomically accurate computer model was generated from detailed computed tomography images and included the vertebral shell, the trabecular centrum, cartilage endplates, intervertebral disks, seven spinal ligament groups, and the facet joints. The cadaveric spinal segment and the specimen-specific finite element model were subjected to various compressive loads ranging from 75 to 975 N using the follower load principle and an oscillating bending moment of +/-5 Nm applied in the sagittal plane. The biomechanical behavior of the finite element model of the spine was validated with the experimental mechanical test data for the corresponding physical thoracolumbar spine specimen. In addition, the effect of intervertebral disk material property variation within the thoracolumbar spinal column on the spinal flexibility was extensively studied. The results of this study provided significant insight into how mechanical properties of the intervertebral disk influence spinal flexibility along the thoracolumbar spinal column. It was found that in order to get comparable results between experimental and computed data, the material properties of the intervertebral disks had to vary along the spinal column. However, these effects are diminished with increasing axial compressive load. Because of the trend between disk properties and spinal level, we further concluded that there might be a mechanism at play that links endplate size, body weight fraction, and segmental flexibility. More studies are needed to further investigate that relationship.
本研究的目的是通过实验和计算来研究椎间盘退变对胸腰椎屈伸灵活性的影响。为此，使用了一个经过七级生物力学测试的人类尸体脊柱（T11-L5）和同一胸腰椎的三维有限元模型。该解剖学精确的计算机模型由详细的计算机断层扫描图像生成，包括椎体壳、小梁中心、软骨终板、椎间盘、七组脊柱韧带和小关节。根据跟随载荷原理，对尸体脊柱节段和特定标本的有限元模型施加75至975 N的各种压缩载荷，并在矢状面施加±5 Nm的振荡弯矩。用相应物理胸腰椎标本的实验力学测试数据验证了脊柱有限元模型的生物力学行为。此外，还广泛研究了胸腰椎柱内椎间盘材料特性变化对脊柱灵活性的影响。本研究结果为椎间盘力学特性如何影响胸腰椎柱的脊柱灵活性提供了重要见解。研究发现，为了在实验数据和计算数据之间获得可比结果，椎间盘的材料特性必须沿脊柱柱变化。然而，随着轴向压缩载荷的增加，这些影响会减弱。由于椎间盘特性与脊柱节段之间的趋势，我们进一步得出结论，可能存在一种机制将终板大小、体重分数和节段灵活性联系起来。需要更多的研究来进一步探讨这种关系。
