摘要
目的探讨退变性腰椎滑脱的应力分布及其变化规律。方法通过CT扫描建立退变性腰椎滑脱节段的有限元力学模型,模拟前屈、中立、后伸3种体位下的加载,计算和分析滑脱节段各部应力分布。结果①腰段脊柱发生滑脱后,下位椎体在Z轴上的应力前移。②椎间盘的剪切应力主要分布在纤维环,前屈时椎间盘纤维环前缘所受剪切应力最大。③无论在前屈位还是在后伸位小关节的平均剪切应力都明显高于椎间盘。左、右侧的小关节的剪切应力相互间也存在着差异。④峡部应力集中,以后伸位时的应力最大,也最具有被破坏的可能性。结论腰椎发生退变性滑脱后,下位椎体对重力的承载部位前移;小关节分布的剪切应力值是椎间盘的72倍,退变的椎间盘与小关节总剪切负荷之比为1∶186,小关节成为剪切应力的主要承载者;峡部具有应力集中,尤以后伸位最显著。
Objective:To inquire into the stress distribution and changes of the degenerative lumbar spondylolisthesis.Methods:A 3D model of the lumbar spondylolisthesis was created according to CT sectional images of the L_4 to L_5 spondylolisthesis,When adding the relative loading on the model,the condition of 3 kinds of postures were imitated,such as flexive,extensive and vertical positions.The stress state of every segment of the L_4 to L_5 spondylolisthesis was calculated and analysed.Results:①After spondylolisthesis generated,the compressive stress mainly distributed in anterior segment of L_5 vertebra.②The shear stress in intervertebral disc mainly distributed in annulus fibrosuses and the shear stress distributed in anterior segment of intervertebral disc were the greatest in vertical condition.③Shear stress on facet joints was greater than that on intervertebral disc in whatever condition.④Von Mises stress on the pars interarticularis was intensive,and the most intensive Von Mises stress in extension,so it was the greatest possibility to be destroyed in extension,Conclusion:After lumbar spine is displacing toward anterior,the compressive stress transfers the posterior parts to the anterior parts of the lower vertebral body.The average shear stress on facet joints is 7.2 times to that on intervertebral disc,the ratio of total shear stress between intervertebral disc and facet joints is 1∶1.86.Shear stress mostly distributed in facet joints.The pars interarticularis has intensive Von Mises stress,and especially the most intensive stress in extension.
出处
《中国骨伤》
CAS
2004年第12期714-716,共3页
China Journal of Orthopaedics and Traumatology
基金
福建省科技三项费用资助项目(K02085)