Sharma M, Langrana N A, Rodriguez J
Department of Mechanical and Aerospace Engineering, Rutgers, State University of New Jersey, New Brunswick, USA.
Spine (Phila Pa 1976). 1995 Apr 15;20(8):887-900. doi: 10.1097/00007632-199504150-00003.
The issue of segmental stability using finite element analysis was studied. Effect of ligament and facet (total and partial) removal and their geometry on segment response were studied from the viewpoint of stability.
To predict factors that may be linked to the cause of rotational instabilities, spondylolisthesis, retrospondylolisthesis, and stenosis.
The study provides a comprehensive study on the role of facets and ligaments and their geometry in preserving segmental stability. No previous biomechanical study has explored these issues in detail.
Three-dimensional nonlinear finite element analysis was performed on L3-L4 motion segments, with and without posterior elements (ligaments and facets), subjected to sagittal moments. Effects of ligament and facet (partial and total) removal and their orientations on segment response are examined from the viewpoint of stability.
Ligaments play an important role in resisting flexion rotation and posterior shear whereas facets are mainly responsible for preventing large extension rotation and anterior displacement. Facet loads and stresses are high under large extension and anterior shear loading. Unlike total facetectomy, selective removal of facets does not compromise segmental stability. Facet loads are dependent on spatial orientation.
Rotational instability in flexion or posterior displacement (retrospondylolisthesis) is unlikely without prior damage of ligaments, whereas instability in extension rotation or forward displacement (spondylolisthesis) is unlikely before facet degeneration or removal. The facet stress and displacement distribution predicts that facet osteoarthritis or hypertrophy leading to spinal stenosis is most likely under flexion-anterior shear loading. Selective facetectomy may restore spinal canal size without compromising the stability of the segment. A facet that is more sagittally oriented may be linked to the cause of spondylolisthesis, whereas a less transversely oriented facet joint may be linked to rotational instabilities in extension.
采用有限元分析研究节段稳定性问题。从稳定性角度研究韧带和小关节（全部和部分）切除及其几何形态对节段反应的影响。
预测可能与旋转性不稳定、椎体滑脱、逆行椎体滑脱和椎管狭窄病因相关的因素。
该研究全面探讨了小关节和韧带及其几何形态在维持节段稳定性中的作用。此前尚无生物力学研究详细探讨过这些问题。
对L3-L4运动节段进行三维非线性有限元分析，分析有无后部结构（韧带和小关节）时矢状面力矩作用下的情况。从稳定性角度研究韧带和小关节（部分和全部）切除及其方向对节段反应的影响。
韧带在抵抗屈曲旋转和后向剪切方面起重要作用，而小关节主要负责防止大幅度伸展旋转和向前移位。在大幅度伸展和前向剪切载荷下，小关节的负荷和应力较高。与全关节突切除术不同，选择性切除小关节不会损害节段稳定性。小关节负荷取决于空间方向。
若无韧带先前损伤，屈曲时的旋转性不稳定或后向移位（逆行椎体滑脱）不太可能发生；而在小关节退变或切除之前，伸展旋转或向前移位（椎体滑脱）时的不稳定也不太可能发生。小关节应力和位移分布预测，在屈曲-前向剪切载荷下，导致椎管狭窄的小关节骨关节炎或肥大最有可能出现。选择性关节突切除术可恢复椎管大小而不损害节段稳定性。矢状面方向更明显的小关节可能与椎体滑脱病因有关，而横向方向不那么明显的小关节可能与伸展时的旋转性不稳定有关。
