LOAD-BEARING ROLE OF FACETS IN A LUMBAR SEGMENT UNDER SAGITTAL PLANE LOADINGS
LOAD-BEARING ROLE OF FACETS IN A LUMBAR SEGMENT UNDER SAGITTAL PLANE LOADINGS
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DOI：
10.1016/0021-9290(87)90281-8
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发表时间：
1987-01-01
影响因子：
2.4
通讯作者：
DROUIN, G
中科院分区：
文献类型：
--
作者：
SHIRAZIADL, A;DROUIN, G
本文应用三维非线性有限元程序，对腰椎I2-3节段小关节的承载作用进行了定量研究。该分析考虑了材料和几何非线性，并将小关节关节视为非线性移动接触问题。椎间盘髓核被认为是一种无粘性不可压缩的流体，而纤维环则被认为是包埋在基质中的胶原纤维的复合物。脊柱韧带被建模为非线性轴向元素的集合。载荷包括轴向压缩、矢状面剪切和弯矩，单独或联合作用。结果表明，在纯压缩状态下，外轴向力主要由椎间盘传递。小关节只承受很小一部分力。然而，小关节在伸展时承受很大的力，而在小屈曲时不承受力。增加压缩会增加伸展时的这些接触力，而对屈曲时的接触力没有影响。在伸展时，小关节上的力通过关节面和囊韧带传递。虽然在小屈曲时小平面不承载载荷，但是当节段屈曲超过7 - 8 °时预计会产生大的接触力。这些力的大小与在大的伸展旋转下计算的力的大小相同，并且几乎在水平面内定向，轴向分量可以忽略不计。在关节连接期间产生的接触力的水平分量通常大于直接抵抗所施加的压缩力的轴向分量。因此，接触力的轴向分量严重低估了作用在小平面上的总力。在屈曲和伸展载荷下，力从一个关节面传递到相邻的关节面是通过不同的区域发生的。也就是说，在上级关节面上，接触区域从大屈曲时的上尖端转移到伸展时的下缘。在下关节面上，接触面积从大屈曲时的上部和中心区域转移到伸展时的下尖端。
In the present work, the load-bearing role of the facet joint in a lumbar I2-3 segment is quantitatively determined by means of a three dimensional nonliner finite element program. The analysis accounts for both material and geometric nonlinearities and treats the facet articulation as a nonlinear moving contact problem. The disc nucleus is considered as an inviscid incompressible fluid and the annulus as a composite of collagenous fibres embedded in a matrix of ground substance. The spinal ligaments are modelled as a collection of nonlinear axial elements. The loadings consist of axial compression and sagittal plane shears and bending moments, acting alone or combined. The results show that in pure compression, the external axial foce is transmitted primarily by the intervertebral disc. The facet joints carry only a small percentage of the force. However, the facet joints carry large forces in extension, whereas in small flexion they carry none. Addition of compression tends to increase these contact forces in extension while it has no effect on them in flexion. In extension, the forces on the facet joints are transmitted by both the articular surfaces and the capsular ligaments. Although in small flexion the facets carry no load, large contact forces are predicted to develop as the segment is flexed beyond 7-8.degree.. These forces are of the same magnitude as those computed under large extension rotation and are oriented nearly in the horizontal plane with negligible component in the axial direction. The horizontal components of the contact forces generated during articulation are often larger than the axial components which directly resist the applied compressive force. The axial components of the contact forces, therefore, grossly underestimate the total forces acting on the facets. The transfer of forces from one facet to the adjacent one occurs through distinct areas in flexion and in extension loadings. That is, on the superior articular surface, the contact area shifts from the upper tip in large flexion to the lower margin in extension. On the inferior articular surface, the contact area shifts from the upper and central regions in large flexion to the lower tip in extension.