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

English Keywords:Artificial vertebral body  Self-stabilizing  Truss structures  Vertebrectomy  Finite element analysis

English Abstract:

  【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.