Study The Effection Of Degenerative Intervertebral Disc On The Stress Distribution Of Lumbar Spine With Three Dimension Finite Element Analysis Method

Objective:To compare the effect of nomal and degenerative intervertebral disc on stress distribution of lumbar spine under five kinds of positions,to explore their biomechanical background and clinical significance and to provide theoretical basis for clinical diagnosis and treatment. Methods rCreating mechanical model of L3-5 motion segment of nomai and degenerative disc with three dimensional finite element method and the five kinds of stress conditions simulated five kinds of physiologic positions was analyzed comparatively. Results:three-dimension finite element model (3D FEM) of L3-5 of nomal and degenerative disc was created, the stress distribution showed some characteristics as follows:(1) With vertical compressive load,lumbar motion segment of nomal disc showed that the stresses of cortical bone were the most intensive,the stresses of end-plate were next to that.A high stress region within cancellous bone made an "I"shape which contained the areas around both end-plates and the central part of vertebral body.In posterior structure of vertebral body,the stress was concentrated at facet joints and pedicles,meanwhile,stress was concentrated on the posterior and posterior-lateral part of annulus fibrosuses.(2) With the changing of position the stress concentrated region varied relatively. (3) comparing the lumbar motion segment of degenerative disc with that of normal disc,the stress distribution changed significantly.The stresses of cortical bone,annulus fibrosus and posterior of vertebral body were elevated,at the same time,the stresses of cancellous bone and nucleus were lowered relatively.(4) In degenerative disc,the effect of changing position on the stress of facet joints and annulus fibrosus was more significante. Conclusion:Creating 3D FEM of L3-5 of nomal and degenerative disc and studying the effect of degenerative disc and changing position on the stress distribution of lumbar spine with 3D finite element method were feasible,and the results were confident.It was significantly different that the influence of degenerative disc and normal disc on the stress distribution of lumbar spine in various positions.The way of transference of load was changed after disc degenerated and position changed.This study helped us correct understanding the pathogenesis of lumbar spine common disorders and direct us to cure these disorders.