Determination of contact force at facet joint with different sagittal orientation under shearing loads:a finite element analysis

[目的]探讨腰椎活动节段关节突矢状方向对关节接触力和接触部位的作用和意义。[方法]采用一种有效的CAD方法精确构建三种关节突矢状方向的三维腰椎L4、5活动节段有限元模型。剪力载荷下，分别对3种有限元模型的关节突接触力和接触部位进行测试。[结果]前剪载荷条件下，关节突接触力随关节突矢状方向角度的增加而减小；后剪载荷下，关节突接触力随关节突矢状方向角度的增加丽增大。前剪和后剪载荷条件下，关节突接触力的矢状和水平分力均随关节突矢状方向角度的减小而增大。相同载荷条件下，不同矢状方向的关节突其接触部位相同。[结论]与矢状型关节突相比，冠状型关节突的空间方向和形态结构对抵抗关节突水平和矢状方向的运动更加有效；前剪载荷较后剪载荷在促进冠状型关节突退变方面起着更为突出的作用。

Determination of contact force at facet joint with different sagittal orientation under shearing loads:a finite element analysis

[Objective] The efleet of sagittal orientations of articular facet on the contact force and contact regions of a lumbar spine segment was evaluated.[Methods] [Results]Three-dimensional geometrical and mechanical accurate finite element models of the lumbar L4、5 motion segment representing three sagittal-orientations articular facet were generated and invalidated by an effective CAD method.Contact force and contact regions of the articular facets of three finite element models were predicted under the pure shearing loads.[Result] Under anterior shear condition,the contact force on the facet decreased with the increase of sagittal 0rientation of articular facet.however.in posterior shear load,the contact force on the facet increased with the increase of sagittal orientation.Meanwhile,under both pure shear loading,the percentages of the sagittal and the transversal components are increased with the dectease of the sagittal angle.However,under the salne load condition,there are no difference between the contact regions of the three models with different facet joint angle.[Conclusion]The spatial orientation and geometric forms of the coronal facet articular surfaces are more effective in restricting motion in transversal and sagittal planes while assuming a minor role in resisting axial force or motion than sagittal facet articular surface.It Was presumed that anterior shear force play a more prominent contribution on the degeneration of the facet joint with coronal articular surface compared with posterior shear force.