腰椎椎间融合联合邻近节段半刚性固定的有限元分析

Finite element analysis of lumbar interbody fusion combined with adjacent-segment semi-rigid fixation

背景:临床中腰椎退行性疾病的发生多伴有多节段病变,为减缓腰椎融合后邻近节段退变,腰椎杂交手术成为一种较好的选择。以往临床观察中WavefleX系统单节段应用取得一定的效果,其在腰椎杂交手术中的应用缺乏生物力学研究结果支持。目的:应用有限元方法分析腰椎融合联合上一位椎体置入WavefleX系统对邻近节段的生物力学影响。方法:利用64排西门子螺旋CT机对静止仰卧志愿者行腰椎薄层扫描,扫描范围为T11-S1,志愿者对实验过程完全知情同意,且得到医院伦理委员会批准。将L3-5水平CT扫描数据依次导入到Mimics医学图像处理软件及Geomagic Studio逆向工程软件中进行处理,于CAD软件SCDM中构建L3-5的腰椎实体模型。在已通过验证的L3-5腰椎模型基础上,分别构建后路椎体间融合模型与Hybrid模型,对3种模型进行赋值和负荷加载,在前屈、后伸、左右侧屈、左右旋转工况下进行有限元分析研究。结果与结论:①在前屈、后伸、侧屈、旋转状态下,相较后路椎体间融合模型,Hybrid模型L3-4椎间盘应力值均有明显减小,后伸状态降幅最大,最大值减少约46%;②各状态下,相较后路椎体间融合模型,Hybrid模型L3-4节段活动度均有明显减小,平均减小约26%,并小于完整模型;③各负荷下,应力云图显示WavefleX系统的连接棒上均有明显的应力集中,双侧的弹性系统的U形开槽凹面处应力明显增大;④位移云图显示,Hybrid模型中WavefleX系统的置入使得其前屈中心后移至弹性结构处;⑤上述结果说明,后路椎体间融合+WavefleX半刚性固定可有效降低上一位邻近节段的椎间盘应力并限其制过度活动,一定程度上维持了腰椎的正常运动特点。

BACKGROUND:The clinical occurrence of lumbar degenerative diseases is often accompanied by multi-segments lesions.To slow down the degeneration of adjacent segments after lumbar fusion,lumbar hybrid surgery has become a better choice.In the past clinical observation,WavefleX system has achieved a certain effect on single segment.Its application in lumbar hybrid surgery lacks the support of biomechanical research results.OBJECTIVE:To analyze the biomechanical effects of lumbar fusion combined with WavefleX system on adjacent segments by the finite element method.METHODS:A 64-row Siemens spiral CT machine was used to scan the lumbar spine of a stationary supine volunteer with a scanning range of T11-S1.This voluntter signed the informed consent.This study was approved by the Hospital Ethics Committee.L3-5 horizontal scanning data were imported into the Mimics medical image processing software and the Geomagic studio reverse engineering software for processing.L3-5 lumbar spine solid model was constructed in the CAD software SCDM.On the basis of L3-5 lumbar model,posterior lumbar interbody fusion model and Hybrid model were constructed respectively.Assignment and load loading were conducted in three models.The finite element analysis was carried out under the conditions of forward flexion,backward extension,lateral flexion and rotation.RESULTS AND CONCLUSION:(1)Compared with posterior lumbar interbody fusion model,the stress value of L3-4 disc in Hybrid model decreased significantly in forward flexion,backward extension,lateral flexion and rotation,and the maximum value decreased about 46%in extension.(2)Compared with posterior lumbar interbody fusion model,the range of motion of L3-4 segment in Hybrid model decreased significantly,with an average decrease of about 26%,which was smaller than that of the complete model under all conditions.(3)Under each load,the stress nephogram showed that there was an obvious stress concentration on the connecting rod of WavefleX system,and the stress at the U-shaped groove concave of the elastic system on both sides was significantly increased.(4)Displacement nephogram showed the placement of WavefleX system in Hybrid model,which made its forward bending center moved back to the elastic structure.(5)The above results show that posterior lumbar interbody fusion+WavefleX semi-rigid fixation can effectively reduce the stress of the last adjacent segment of the disc and limit the excessive activity,maintain the normal movement characteristics of the lumbar spine to a certain extent.