腰椎后路椎间植骨融合内固定术后邻近节段椎间盘退行性改变生物力学特点的有限元分析

目的采用有限元方法分析腰椎后路椎间植骨融合内固定术后邻近节段椎间盘退变的生物力学特点。方法采集1名正常成人L_3~5的CT扫描数据,经有限元软件建立正常腰椎L_3~5模型(正常模型)、L_4、5椎弓根钉内固定模型(PSF),以及L_4、5全椎板减压、椎间cage融合、椎弓根钉内固定模型(PSF+PLIF)。比较3个模型在模拟人体腰椎前屈、后伸、左侧弯、右侧弯、左轴向旋转、右轴向旋转时L_3、4椎间盘膨出与内陷最大值,以及各方向L_3、4纤维环应力峰值。结果 PSF+PLIF模型与PSF模型L_3、4椎间盘膨出、内陷最大值较正常模型明显增大,且PSF+PLIF模型较PSF模型大,差异有统计学意义(P <0.05)。PSF+PLIF模型与PSF模型左侧弯、右侧弯、左轴向旋转、右轴向旋转时L_3、4的纤维环应力峰值增幅明显大于Model模型,且PSF+PLIF模型增幅大于PSF模型,差异有统计学意义(P <0.05)。结论腰椎后路椎间植骨融合内固定术引起邻近节段椎间盘生物力学改变是加重邻近节段椎间盘退行性改变程度的重要因素。

Finite element analysis of biomechanical characteristics of disc degenerative changes in adjacent segments after posterior lumbar intervertebral bone fusion and internal fixation

Objective To analyze the biomechanical characteristics of lumbar intervertebral disc degeneration in adjacent segment after posterior lumbar intervertebral bone fusion and internal fixation by finite element method.Methods CT scan data of lumbar3~5(L3~5)in one normal adult were collected.Normal Model(Model)of L3~5 vertebrae,pedicle screw internal fixation Model of L4、5(PSF)and total laminar decompression of L4、5,interbody cage fusion,pedicle screw internal fixation model(PSF+PLIF)were established by finite element software processing.The maximum values of L3、4 intervertebral disc bulging and invagination when simulating human lumbar vertebra forward flexion,extension,left bend,right bend,left axial rotation,right axial rotation were compared as well as the stress peaks of L3、4 fiber ring stress in all directions.Results Bulging and invagination of L3、4 intervertebral disc had significantly higher maximum values in the PSF+PLIF Model and the PSF Model than in the Model,meanwhile in the PSF+PLIF Model than in the PSF Model under the same loading situations,with statistically significant differences(P<0.05).In the condition of flexion,extension or lateral bending,the stress peaks of L3、4 fiber ring were stronger in the PSF+PLIF Model and the PSF Model than that in the Model,meanwhile also stronger in the PSF+PLIF Model than in the PSF Model,and there were all statistically significant differences(P<0.05).Conclusion The biomechanical changes of the intervertebral discs in the adjacent segments caused by the posterior lumbar intervertebral bone fusion and internal fixation are important factors that aggravate the degree of degenerative changes in the adjacent discs.