三种骨水泥弥散类型对胸腰段椎体强化术后术椎应力影响的三维有限元分析

Three-dimensional finite element analysis of the influence of three subtypes of bone cement distribution on the postoperative stress of thoracolumbar vertebral body

中文关键词:  骨水泥  弥散类型  椎体强化术  有限元

英文关键词:Bone Cement  Diffusion Type  Vertebroplasty  Finite Element

中文摘要:

  【摘要】 目的：利用三维有限元分析胸腰段椎体强化术后三种骨水泥弥散类型在不同载荷下术椎的应力分布变化。方法：通过1例L1椎体压缩性骨折患者和3例L1椎体强化术后骨水泥分别呈弥散型、团块型、混合型患者的原始CT资料，通过Mimics 19.0、Geomagic Studio 2013及 Solid Works 2017等软件处理，建立T11～L2椎体功能单元压缩性骨折及三种骨水泥弥散类型的有限元模型，运用有限元分析方法，约束L2椎体下表面所有节点的各向活动，于T11椎体上表面施加均匀分布的400N面载荷，压力方向垂直向下，模拟正常人体上半身重量；同时在T11椎体上表面于不同方向施加10N·m力矩，模拟正常人体前屈、后伸、左侧屈、右侧屈、左旋转、右旋转6种运动状态。并在T11表面分别施加0.3MPa（低压力）、1MPa（中压力）、4MPa（高压力）分别模拟日常生活活动，比较4种模型在不同载荷情况下应力分布情况。结果：骨水泥注入后，在各级压力下，骨水泥呈团块型分布对术椎应力明显高于弥散型与混合型，4种模型术椎的应力与压力增加呈正相关，在6种载荷下，骨水泥呈团块型分布对术椎的应力均明显高于混合型与弥散型，混合型对术椎的应力较低，且在施加0.3、1、4MPa压力下，术椎在前屈载荷下所受应力最大，团块型应力最高，分别为63.295MPa、84.419MPa、174.96MPa;弥散型为62.348MPa、80.974MPa、160.95MPa、混合型为47.667MPa、62.171MPa、124.35MPa。结论：胸腰段椎体强化术后术椎应力与其所受压力及载荷方向相关，团块型骨水泥是导致术椎应力增高的重要因素，骨水泥呈混合型分布可能是理想的弥散类型。

英文摘要:

  【Abstract】 Objectives: Using finite element method to analyze the distribution changes of stress under different loads in three subtypes of diffuse-type bone cements after thoracolumbar vertebroplasty. Methods: To establish the finite element models of T11-L2-vertebral-function-unit compression fracture and three subtypes of diffuse-type bone cement based on the CT source data of bone cement of 1 patient with L1 spinal compression fracture and 3 patients undergone L1 vertebroplasty, presenting diffuse subtype, bulk subtype and mixed subtype respectively, and computed by Mimics 19.0, Geomagic Studio 2013, and Solid Works 2017 software. Using the method of finite element analysis, to simulate the weight of the upper half of a normal person after limited every activity of all the nodes under the L2 vertebral surface, and applied evenly 400N surface load on the T11 vertebra, with vertically downward pressure. At the same time, 10N·m torque was applied on the surface of the T11 vertebra with different directions, to simulate 6 movement conditions, namely anterior flexion, posterior extension, right-side bending, left-side bending, left lateral rotation and right lateral rotation. Also, pressure of 0.3MPa(lying flat), 1MPa(standing), and 4MPa(loading) were applied respectively on the T11 surface to simulate daily-life activities. The stress distribution of the 4 models under different load conditions was observed. Results: After the injection of bone cement, under different levels of pressures, the distribution, regarding the operated vertebra, of the bulk subtype bone cement was significantly higher than that of the diffuse subtype and mixed subtype. The stress of the operated vertebra showed a positive correlation to the increase of the pressure in 4 types of models. For 6 movement conditions, the distribution, regarding the operated vertebra, of the bulk subtype bone cement was significantly higher than that of the diffuse subtype and mixed subtype, and the stress of the operated vertebra of the mixed subtype was relatively lower. After applications of 0.3, 1, and 4MPa pressure, the operated vertebra with anterior flexion encountered the maximum stress, and the stress of the bulk subtype was the highest, which were 63.295MPa, 84.419MPa and 174.96MPa respectively, while that of the diffuse subtype were 62.348MPa, 80.974MPa and 160.95MPa, and that of the mixed subtype was 47.667MPa, 62.171MPa and 124.35MPa. Conclusions: The stress of the post-vertebroplasty vertebra is correlated to the pressure and the load directions. Bulk subtype bone cement is an important factor leading to the increase in stress of the operated vertebra. Bone cement with mixed subtype distribution is possibly a more ideal diffuse type.