伤椎椎弓根置钉治疗胸腰椎压缩性骨折的三维有限元分析*

背景：有文献报道伤椎置钉技术较传统4钉跨阶段固定具有更强的牢固性，可有效避免内固定的松动断裂，但其生物力学机制研究尚显不足。 目的：构建脊柱胸腰椎单纯压缩性骨折的三维有限元模型，探讨伤椎附加椎弓根螺钉置入治疗胸腰椎压缩性骨折的生物力学效应。 方法：将一T12椎体压缩性骨折患者脊柱胸腰段超薄CT扫描数据输入Mimics软件中，构建T12椎体压缩性骨折的有限元模型，在此模型基础上模拟伤椎置6钉和跨节段4钉内固定，对两个模型分别施加垂直压缩、前屈、后伸、左屈及右旋载荷。 结果与结论：两组固定模式各种载荷下的应力均集中在螺钉根部，在垂直载荷下，螺钉的应力最小，右旋和左屈载荷下的应力最大；在垂直压缩、前屈、后伸、左侧弯及右旋运动下，上位螺钉较下位螺钉应力大(P < 0.05)。伤椎置6钉固定组螺钉应力较跨节段4钉固定组小(P < 0.05)。两组T11椎体最大位移无差别。表明伤椎附加椎弓根螺钉置入可以优化内固定的载荷，减少断钉率。

Treatment of thoracolumbar fractures by vertebral pedicle-screws through the fractured vertebrae based on a three-dimensional finite element method

BACKGROUND: It has recently been reported in the literature that segmental fixation with screws at the level of the fracture achieves improved stability over conventional four-screw fixation because it effectively reduces the incidence of screw loosening and internal fixation fracture, but the research about the biomechanics is inadequate. OBJECTIVE: To construct a three-dimensional finite element model of thoracolumbar vertebral compression fractures and to investigate the biomechanical mechanism of the treatment about thoracolumbar vertebral compression fractures with pedicle screws in injured level. METHODS: The ultrathin CT scan data obtained from one young male patient with the compression fractures of T12 were put into the Materialise Mimics to reconstruct a compression fracture model of T12. The fracture model was treated respectively with six and four pedicle screws. Vertical compression, flexion, extension, left and right bending loadings were performed. RESULTS AND CONCLUSION: The largest stress was measured in the screw root. The stress under the vertical loading was the lowest, while those under the right bending and left flexion loadings were the highest. The stress of the superior screw was larger than that of the subordinate screw (P < 0.05). The stress in the four-screw group was larger than that in the six-screw group (P < 0.05). The maximal deflection of T11 under different loadings had no difference between the two groups. It is indicated that it can be optimized to reduce the failure of internal fixation with pedicle screws in injured level.