骨水泥注射体积与骨质疏松压缩性骨折椎体及邻近椎体应力的关系

背景：椎体成形及椎体后凸成形可有效修复骨质疏松性椎体压缩性骨折，但术后可引起骨折椎体及邻近椎体应力改变易导致新发骨折。目的：应用三维有限元法分析椎体成形不同体积骨水泥注射后骨折椎体及邻近椎体的应力变化。方法：选取1例有代表性的健康成年男性志愿者行腰椎CT扫描，将图像处理后导出应用Mimics进行三维重建，应用Geomagic对三维模型进行光滑、打磨、去噪，Ansys Workbench下装配实体模型，赋值后建立L2-L4段骨质疏松椎体压缩性骨折模型。设定在L3椎体注入分别1 mL、2 mL、4 mL、6 mL骨水泥，骨水泥在椎体中央呈球形分布。在L2上表面施加500 N预载荷，附加弯矩为50 N•m，约束L4下表面自由度。模拟L2-L4前屈、后伸、右屈及右侧轴向旋转4种运动状态，比较不同体积骨水泥注射前后骨折椎体及上下邻近椎体的应力变化。结果与结论：骨折椎体及邻近椎体应力骨水泥注射后均较注射前明显增加，并随骨水泥注入量的增加骨折椎体及邻近椎体承受的应力也随之增大，其可能是导致邻近椎体骨折的因素之一。 中国组织工程研究杂志出版内容重点：生物材料；骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性；组织工程 

Relationship of bone cement injection volume with the stress of osteoporotic compression fractured and adjacent vertebrae

BACKGROUND: Vertebroplasty and kyphoplasty can effectively repair osteoporotic vertebral compression fractures, but postoperative change of stress in the fractured vertebrae and adjacent vertebrae can lead to new fractures.OBJECTIVE: To analyze the stress changes of the fractured and adjacent vertebrae with different bone cement injection volume by three-dimensional finite element method.METHODS: One healthy adult male volunteer was selected for lumbar spine CT scan. The acquired images were  imported for three-dimensional reconstruction using Mimics. The three-dimensional model was smoothed, polished and denoised by Geomagic software, and then the solid mode was built under Workbench Ansys. The osteoporotic vertebral compression fracture model in L2-L4 segments was established after assignment. Bone cement of 1, 2, 4, 6 mL was injected into the L3 vertebrae respectively and distributed in the middle of the vertebrae as spherical shape. 500 N pre-load was applied on L2 surface with an additional moment of 50 N•m. The lower surface free degree of L4 was restrainted. The L2-L4 forward flexion, extension, right flexion and axial rotation on the right side were stimulated to compare the stress changes of fractured vertebrae and adjacent vertebrae before and after the bone cement injection with different volume. RESULTS AND CONCLUSION: The stresses of fractured and adjacent vertebrae after the bone cement injection were significantly increased; meanwhile, the stresses of fractured and adjacent vertebrae increased with the increase of bone cement injection volume, which may be one of the factors leading to the compression fractures of adjacent vertebrae.