定量CT有限元分析椎体强化对不同位置非强化椎生物力学参数的影响

Effect of vertebral augmentation using quantitative computed tomography-based finite element analysis on biomechanical parameters of non-enhanced vertebrae in different locations

背景:骨水泥与骨质疏松椎体间在生物力学特性上的巨大差异是否会增加再骨折的发生还存有争议。骨水泥的置入将导致多大范围的非强化椎生物力学参数改变仍然不清楚。目的:通过以定量CT为基础的长节段骨质疏松性椎体压缩骨折有限元模型,分析椎体强化对于骨质疏松脊柱生物力学参数的影响范围。方法:以定量CT数据为基础构建T4-L5长节段T12椎体骨质疏松性压缩骨折模型,在对模型施加150 N垂直载荷的基础上,沿不同方向分别施加1.5 N·m的扭力矩以模拟前屈、后伸、左右侧屈及左右旋转状态,比较骨水泥置入前后模型椎体、椎间盘及小关节的应力变化。结果与结论:(1)模型骨水泥置入后,各个运动状态下整体位移幅度平均下降约16%;(2)强化椎近端5个椎体应力较术前平均增加约20%,头端第一椎间盘应力较术前下降约20%,第二、第三椎间盘应力则分别增加约4%及2%;强化椎及其尾端邻椎小关节应力较术前下降约6%,其余尾端小关节及头端相邻4个节段小关节应力均较术前不同程度增加;并且这种应力改变均表现为距强化椎越近变化越显著的趋势;(3)结果表明椎体强化将导致强化椎头尾端多个椎体、椎间盘及小关节应力的显著改变,且距强化椎越近改变越明显,这种应力改变可能与椎体强化后再骨折的发生有关。

BACKGROUND:Whether the huge difference in biomechanical properties between bone cement and osteoporotic vertebral body will increase the occurrence of refracture is still controversial.The extent to which cement implantation will affect the biomechanical parameters of unaugmented vertebrae remains unclear.OBJECTIVE:To analyze the influence range of vertebral augmentation on biomechanical parameters of the osteoporotic spine through the finite element model of long-segment osteoporotic vertebral compression fracture based on quantitative CT.METHODS:The osteoporotic compression fracture model of T12 vertebrae with a long segment of T4-L5 was constructed based on quantitative CT data.On the basis of 150 N vertical load,1.5 N•m torsional torque was applied to the model in different directions to simulate flexion,extension,lateral flexion and rotation.The stress changes of the vertebral bodies,intervertebral disc and facet joint were compared before and after bone cement implantation.RESULTS AND CONCLUSION:(1)After implantation of model bone cement,the overall displacement amplitude of each movement state decreased by 16%on average.(2)The stress of the fifth vertebrae away from the treated vertebra at the cephalic side increased by approximately 20%on average;the stress of the first intervertebral disc at the cephalic side decreased by approximately 20%,and the stress of the second and third intervertebral discs increased by approximately 4%and 2%,respectively.The stress of the facet joints of the treated vertebrae and its caudal adjacent vertebrae decreased by approximately 6%,and the stress of the other caudal facet joints and the four cephalic adjacent facet joints increased to different degrees.In addition,the stress changes tended to be more significant the closer to the treated vertebra.(3)The results of this study show that the stress of multiple vertebral body,intervertebral discs and facets at the cephalic and caudal sides from the augmented vertebra will be significantly changed by cement implantation,and the closer to the treated vertebra,the more obvious the effect is.This stress change may be associated with the occurrence of new fractures after vertebral augmentation.