后凸成形术中骨水泥量对相邻椎体终板影响的有限元分析

Finite element analysis of cement volume affecting adjacent vertebral endplate in percutaneous kyphoplasty

目的通过分析后凸成形术中不同容积的骨水泥填充量对相邻椎体终板应力的影响，探讨后凸成形术后相邻椎体骨折发生的可能机制。方法建立胸腰段脊柱骨质疏松性椎体压缩骨折三维有限元模型，模拟经皮后凸成形术（percutaneouskyphoplasty，PKP）对椎体进行部分复位（80％），分别在骨折椎体内植入两种剂量（4．0ml填充15％椎体容积，8．0ml填充30％椎体容积）骨水泥进行填充，分析轴向压缩、前屈和后伸三种情况下相邻椎体终板应力的变化情况。结果比较PKP术中两种填充剂量下相邻椎体终板在各种情况下的应力差别，发现T11椎体下位终板与L1椎体上位终板总体应力均较术前增加，并与骨水泥充填量呈正相关，且应力主要集中在终板前部和中部。结论PKP术后相邻椎体终板应力的增加与骨水泥充填量呈正相关，且以终板前中部为应力集中部位。随着骨水泥填充量的增加，PKP术后相邻椎体骨折概率呈增高趋势。

Objective To analyze the stress contribution of different cement volume to the adja- cent vertebral endplates in percutaneous kyphoplasty （PKP） so as to explore the possible mechanism of adjacent vertebral fractures after PKP. Methods The three-dimensional finite element model of osteo- porotic thoracolumbar vertebral compression fractures was established to simulate vertebral body partial restoration （80%） with PKP. During the process, two doses of bone cement （polymethylmethacrylate, PMMA） were filled in the vertebral body （4.0 ml bone cement filling 15% of the vertebral body volume and 8.0 ml bone cement filling 30% of the vertebral body volume）. Endplate stress under conditions of axial compression, flexion and extension was analyzed. Results Regarding the two filling doses in PKP, the adjacent vertebral endplate stress under the above-mentioned conditions was all increased at T^1 and L~ vertebral body compared with that before operation. Meanwhile, endplate stress had positive corre- lation with the cement volume and the stress concentrated largely in the anterior and middle parts of end- plate. Conclusions The stress of adjacent vertebral endplate is positively correlated with cement vol- ume, with anterior and middle parts of endplate as the stress concentration. The probability of adjacent vertebral fractures shows a rising trend with the increase of cement volume in PKP.