新型腰椎后路动态稳定系统的三维有限元分析

The three-dimensional finite element analysis of the dynamic stable system of the new lumbar spine

目的对新型腰椎后路动态稳定系统进行三维有限元分析,研究其在稳定节段及邻近节段的生物力学影响,为下腰痛的脊柱内植物的设计和应用提供参考。方法基于正常腰椎有限元模型,构建腰椎不稳损伤模型,即腰椎切除腰4和腰5之间的双侧小关节、腰4椎板下1/2、后纵韧带,形成脊柱失稳模型,分别在失稳模型上进行坚强内固定系统和后路动态稳定系统,比较两种术式对手术节段和临近阶段的活动度、各个节段的弯曲刚度、椎间盘应力水平、前纵韧带应力水平及小关节韧带拉力的变化情况。结果对内固定桥接节段(腰4/腰5)应用新型腰椎后路动态稳定系统和坚强内固定系统后,在屈伸、侧屈、轴向旋转方向上的活动度均明显减小,但坚强固定后活动度减小更明显,应用动态稳定系统活动度更接近于正常腰椎节段;腰4/腰5椎间盘最大应力均减小,但坚强固定后活动度减小更明显,应用动态稳定系统活动度更接近于正常腰椎节段;对邻近节段(腰3/腰4、腰5/S1)应用新型腰椎后路动态稳定系统和坚强内固定系统后,在屈伸、侧屈、轴向旋转方向上的活动度均有所增大,但坚强固定后活动度增加更明显,应用动态稳定系统邻近节段活动度更接近于正常腰椎节段;邻近节段椎间盘最大应力均增大,但坚强固定后增大更明显,应用动态稳定系统更接近于正常腰椎节段;应用腰椎内固定后,邻近节段的小关节应力峰值增大,并且应用腰椎坚强内固定模型的小关节应力增大更多;应用腰椎动态固定的模型邻近关节应力峰值更加接近完整腰椎模型。结论新型腰椎后路动态稳定系统对比坚强内固定系统能够使失稳节段的活动更加接近于正常,减小邻近节段的活动度增加,减小邻近节段椎间盘及小关节压力,说明新型腰椎动态稳定系统达到设计要求。

Objective A three-dimensional finite element analysis of the dynamic stability system of the new lumbar spine was studied,which also focused on the biomechanical effects of the stable segment and adjacent segment.Methods Based on the finite element model of lumbar vertebra,the model of lumbar instability damage was constructed.With resection on the lumbar spine model between L4 and L5 on both sides of the small joints,waist 4 longitudinal ligament and vertebral plate under 1/2,a spinal instability model was built,on which a pedicle screw system and a posterior dynamic stabilization system were added respectively.Then we compared how they were influenced by surgical operation sections and adjacent stages of activity,the bending stiffness of each section,intervertebral disc stress levels,anterior longitudinal ligament stress levels and the changes of the small joint ligament strain.Results For internal fixation of bridge section(L4/L5),after the new lumbar posterior dynamic stabilization and rigid internal fixation systems were applied,the activity of it in the directions of flexion,lateral bending and axial rotation was significantly decreased,but the activity decreased more obviously under the posterior dynamic stabilization system while it was closer to the normal one under the lumbar posterior dynamic stabilization system;the maximum stress of L4/L5 intervertebral disc decreased,but the decrease of the activity degree of strong fixation was more obvious,whereas that of the dynamic stable system was more similar to the normal lumbar segment.For adjacent segment(L3/L4,L5/S1),with application of the two systems,the activity of it in the directions of flexion,lateral bending and axial rotation has increased,but the activity increased more obviously under the posterior dynamic stabilization system while it was closer to the normal one under the lumbar posterior dynamic stabilization system;the maximum stress of intervertebral disc in adjacent segment increased,but the increase of the activity degree of strong fixation was more obvious,whereas that of the dynamic stable system was more similar to the normal lumbar segment.The stress peak of small joints in adjacent segment increased under the rigid internal fixation system with the stress of small joints increasing more while the stress peak of the adjacent joints was closer to the complete lumbar model under the lumbar posterior dynamic stabilization system.Conclusions Compared with the strong internal fixation system,the new lumbar posterior dynamic stability system can make the instability of segmental activity closer to the normal,reduce the increase of adjacent segment activity as well as the pressure of adjacent segment disc and small joints,which suggests that the new lumbar dynamic stability system has met the design requirements.