| Objective: To establish a three-dimensional finite element model of type IIIa lumbosacral transitional vertebrae(LSTV)using finite element technique and evaluate the biomechanical characteristics of the transitional vertebrae and their adjacent segments.This provides a reference for the waist activity of LSTV patients.Methods: A 30 years old,the imaging diagnosis of lumbar disease excluded healthy volunteers.Using SIEMENS 64 slice spiral CT scanning was performed in all the lumbar segment and part of the sacral segment,0.625 mm thick layer of CT images,and then using medical image processing software Mimics17.0 for processing image data.Then using Geomagic9.0 to establish geometric model,set the boundary conditions and under the same load,the establishment of normal lumbar spine model.Based on the normal lumbar spine model,the establishment of a type Ⅲa lumbosacral vertebral fusion model.Finally,introducing the Abaqus 13 finite element analysis software.The sacrum is fixed at the lower end,1 in lumbar endplate of the vertebral body longitudinal pressure load 500 N,then simulate the lumbar flexion,extension,lateral bending and rotation movement,comparing the two models of adjacent segment 4/5lumbar,lumbar 5 sacral 1 disc fibrous ring and 5 lumbar transverse root stress.Results: The average stiffness of the lumbar finite element model established in this experiment was similar to that reported previously.In left and right rotation and left and right lateral bending,the type IIIa LSTV stress mainly concentrated at the root of the lumbar 5 vertebrae at the fusion site,and the stress increased by 815.49%,516.84%,290.00%,and 197.85%,respectively,compared with the normal group.The stress of the lumbar intervertebral disc annulus fibrosis was increased by 15.16%,1.66%,20.63% and 14.31%,respectively,compared with the normal group.However,the stress of the 4/5 disc annulus was reduced by 16.66%,16.00%,17.21%,and 19.16%compared with the normal group.Conclusion:Compared with the normal model,the pressure of the IIIa LSTV model,at the rotation and lateral bending L5/S1 annulus fibrosus and fusion site of the proximal segment,was increased.On the contrary,the pressure of normal model at flexion and dorsal extension was higher then that of the IIIa LSTV model.Therefore,the patients with LSTV should less lumbar lateral curvature and rotation,and degenerative pressure of LSTV changes in the adjacent segment. |
