不同形态结构3D打印钛合金人工椎体在全脊椎切除术后应用的生物力学特性有限元分析

Finite element analysis of the biomechanical properties of 3D-printed artificial vertebral bodies of titanium alloy with different morphological structures implanted after total en bloc spondylectomy

中文关键词:  人工椎体  自稳结构  桁架结构  全脊椎切除术  有限元分析

英文关键词:Artificial vertebral body  Self-stabilizing  Truss structures  Vertebrectomy  Finite element analysis

中文摘要:

  【摘要】　目的：比较标准、自稳及桁架三种形态结构的3D打印钛合金人工椎体（artificial vertebral body，AVB）在全脊椎切除术后重建中的生物力学特性。方法：基于健康成年男性T10~L2节段CT数据构建正常脊柱有限元模型并进行验证，移除T12椎体模拟全脊椎切除术后缺损，分别置入标准（圆柱形）、自稳（上下端两对螺钉）及桁架（两侧带钉棒连接环孔）三种形态结构的3D打印钛合金AVB，通过Abaqus软件施加200N轴向载荷及7.5N·m扭矩模拟前屈、后伸、侧弯及旋转运动，分析“椎体-假体-椎体”复合结构的整体刚度和后柱连接杆、终板及融合器的应力分布情况。结果：本研究建立的T10~L2正常脊柱有限元模型活动度与既往文献报道一致，模型有效。刚度分析显示，标准结构、桁架结构及自稳结构AVB在相同载荷下位移差异均≤0.1mm，其中自稳结构位移最小；桁架结构在左右侧弯运动时位移更小。后柱连接杆应力结果表明，三种形态结构AVB的后柱连接杆均在旋转运动中承受最大Von Mises应力（174.90~175.00MPa）；与标准结构相比，桁架结构在屈伸及侧弯运动时后柱连接杆中段应力降低18.5%~24.3%。终板应力分析显示，前屈运动时终板Von Mises应力最大，标准结构、桁架结构及自稳结构的应力值分别为32.54MPa、30.76MPa及24.37MPa；自稳结构终板应力较其他两种结构分别减小14%~30%。内固定系统应力分析表明，自稳结构AVB的应力显著低于标准结构AVB及桁架结构AVB，其中前屈运动中分别减少57%、61%；侧弯运动中分别减少52%~62%、59%~64%；旋转运动中分别减少61%~62%、46%~61%。结论：相较于标准结构AVB，桁架结构AVB可通过多段应力分散机制降低后柱连接杆应力集中；自稳结构AVB通过螺钉固定可增强假体-椎体界面稳定性。

英文摘要:

  【Abstract】 Objectives: To compare the biomechanical characteristics of 3D-printed titanium alloy artificial vertebral bodies(AVB) with standard, self-stabilizing, and truss structures in spinal reconstruction after total en bloc spondylectomy(TES). Methods: A finite element model of the normal spine was constructed based on the CT data of the T10-L2 segments of a healthy adult male and was subsequently validated. The defect after vertebral column resection was simulated by removing the T12 vertebra, and three types of 3D-printed titanium alloy AVBs were implanted: standard(cylindrical), self-stabilizing(with two pairs of screws at the upper and lower ends), and truss(with bilateral ring holes for screw-rod connection). A 200N axial load and a 7.5N·m torque were applied using Abaqus software to simulate flexion, extension, lateral bending, and rotation movements. The overall stiffness of the "vertebra-prosthesis-vertebra" composite structure, the stress distributions on the posterior column connecting rod, the endplate, and the fusion device were analyzed. Results: The range of motion of the T10-L2 normal spinal finite element model established in this study was consistent with previous literature reports, therefore validating the model. Stiffness analysis showed that the displacement difference among the standard, truss, and self-stabilizing AVBs under the same load was ≤0.1mm, with the self-stabilizing structure AVB exhibiting the smallest displacement; The truss structure had smaller displacement in left-right bending. Stress analysis results indicated that the posterior column connecting rods of the three kinds of morphological AVBs bore the maximum Von Mises stress(174.90-175.00MPa) during rotation. Compared with the standard structure, the truss structure reduced the mid-segment stress of the posterior column connecting rod by 18.5%-24.3% during flexion-extension and lateral bending. Endplate stress analysis revealed that the maximum Von Mises stress on the endplate occurred during flexion, with values of 32.54MPa, 30.76MPa, and 24.37MPa for the standard, truss, and self-stabilizing structures, respectively. The self-stabilizing structure reduced endplate stress by 14%-30% compared with the other two structures. Analysis of the internal fixation system showed that the cage stress of the self-stabilizing AVB was significantly lower than that of the standard and truss structures: reduced by 57% and 61% in flexion; 52%-62% and 59%-64% in lateral bending; and 61%-62% and 46%-61% in rotation, respectively. Conclusions: Compared to the standard structure, the truss structure AVB reduces the stress concentration of the posterior column connecting rod through a multi-segment stress dispersion mechanism. The self-stabilizing structure AVB enhances the stability of the prosthesis- vertebral body interface through screw fixation.