腰椎后外侧融合椎弓根钉对相邻节段椎间盘影响的三维有限元分析

摘要

Objective To analyze the effect of pedicle screw implant location on the stress of adjacent segment intervertebral discs under different conditions with three dimensional finite element. Methods Normal lumbosacral vertebral(L3-S1) model of a healthy adult male was established using digital software. Fusion model A,B,C were set up respectively according to the pedicle screw position by dividing the vertebral body into trisection. Corresponding load and torque were applied on the 3 different models according to different conditions to obtain the stress changes of the intervertebral disc that happened to the adjacent segments. Results Normal three-dimensional finite element model of normal(L3-S1) and posterior lumbar laminectomy and pedicle screw fixation(models A,B,C) were established successfully. In retroflexion condition,the stress of L3/L4 in model A significantly increased,while no significant change in models B and C. In bending condition,the stress of L3/L4 in model A significantly increased,while little change in models B and C. In the rest conditions,the stress of L3/L4 in the 3 models all increased,especially in model A. In all conditions,the stress of L5/S1 in the 3 models all slightly increased,and the changes of the models B and C were smaller than that of the model A. Conclusion Implanting pedicle screw tip into the upper area of the vertebral body could increase the stress of the upper adjacent disc,which may result in postoperative adjacent segment degeneration. However,lumbar fusion surgery do not obviously increase the stress of the lower adjacent intervertebral disc.%目的：利用三维有限元法分析腰椎不同运动状态时椎弓根钉的置入位置对邻近节段椎间盘应力的影响。方法利用三维建模软件建立正常人有效性腰骶椎（L3~S1）模型。根据椎弓根钉在椎体的位置，分别建立融合模型A、B、C。并根据不同工况对这3种模型施加相应的预载荷及扭矩，分析比较不同腰椎轴向运动时相邻节段椎间盘应力的变化情况。结果成功建立正常有效的L3~S1三维有限元模型及椎弓根钉棒系统融合固定三维有限元模型。在后伸状态下，模型A的L3/L4椎间盘应力明显增加，而模型B、C较融合前无明显变化；在侧曲状态中，模型B、C的L3/L4椎间盘应力变化不大，而模型A显著增加；在其余状态中，3个模型的L3/L4椎间盘应力均升高，其中以模型A增加最为明显。3个模型在所有状态下L5/S1椎间盘的应力均较融合前略有升高，其中模型B、C应力的变化小于模型A。结论椎弓根钉尖端位于椎体上1/3区域会显著增加融合节段上位邻近椎间盘应力，进而引起相邻节段退变；腰椎融合术不会明显增加邻近下位椎间盘的应力。