Schmidt Hendrik, Kettler Annette, Rohlmann Antonius, Claes Lutz, Wilke Hans-Joachim
Institute of Orthopaedic Research and Biomechanics, University of Ulm, Helmholtzstrasse 14, D-89081 Ulm, Germany.
Clin Biomech (Bristol). 2007 Nov;22(9):988-98. doi: 10.1016/j.clinbiomech.2007.07.008. Epub 2007 Sep 5.
Disc prolapses can result from various complex load situations and degenerative changes in the intervertebral disc. The aim of this finite element study was to find load combinations that would lead to the highest internal stresses in a healthy and in degenerated discs.
A three-dimensional finite element model of a lumbar spinal segment L4-L5 in different grades of disc degeneration (healthy, mild, moderate, and severe) were generated, in which the disc height reduction, the formation of osteophytes and the increasing of nucleus' compressibility were considered. The intradiscal pressure in the nucleus, the fiber strains, and the shear strains between the annulus and the adjacent endplates under pure and complex loads were investigated.
In all grades of disc degeneration the intradiscal pressure was found to be highest in flexion. The shear and fiber strains predicted a strong increase under lateral bending+flexion for the healthy disc and under axial rotation and lateral bending+axial rotation for all degenerated discs, mostly located in the postero-lateral annulus. Compared to the healthy disc, the mildly degenerated disc indicated an increase of the intradiscal pressure and of the fiber strains, both of 25% in axial rotation. The shear strains showed an increase of 27% in axial rotation+flexion. As from the moderately degenerated disc all measurement parameters strongly decreased.
The results support how specifically changes associated with disc degeneration might contribute to risk of prolapse. Thus, the highest risk of prolapses can be found for healthy and mildly degenerated discs.
椎间盘突出可由各种复杂的负荷情况和椎间盘的退行性变引起。本有限元研究的目的是找出能导致健康椎间盘和退变椎间盘中产生最高内部应力的负荷组合。
建立了不同退变程度（健康、轻度、中度和重度）的腰椎L4-L5节段的三维有限元模型，其中考虑了椎间盘高度降低、骨赘形成和髓核可压缩性增加。研究了单纯负荷和复合负荷下髓核内压力、纤维应变以及纤维环与相邻终板之间的剪切应变。
在所有退变程度的椎间盘中，发现髓核内压力在屈曲时最高。对于健康椎间盘，剪切应变和纤维应变预测在侧屈+屈曲时会大幅增加；对于所有退变椎间盘，在轴向旋转以及侧屈+轴向旋转时会大幅增加，大部分位于后外侧纤维环。与健康椎间盘相比，轻度退变椎间盘在轴向旋转时髓核内压力和纤维应变均增加25%。在轴向旋转+屈曲时，剪切应变增加27%。从中度退变椎间盘开始，所有测量参数均大幅下降。
结果支持了与椎间盘退变相关的特定变化如何可能导致突出风险。因此，健康和轻度退变的椎间盘突出风险最高。
