Finite element analysis of the mechanical properties of 3D-printed artificial vertebral body of PEEK matrix composites

English Keywords:Artificial vertebral body  Polyetheretherketone  Finite elements  Stress occlusion rate

English Abstract:

  【Abstract】 Objectives: To analyze the mechanical properties of the personalized artificial vertebral body of 3D-printed polyetheretherketone(PEEK) matrix composites after implantation and its effect on adjacent tissues using finite element analysis. Methods: The CT scan data of a healthy male volunteer was extracted for 3D reconstruction, the finite element model of the lumbar spine(L1-L5) was constructed, and the ranges of motion of different lumbar vertebrae segments in various motion states were simulated, after that, the effectiveness of the finite element model was verified by comparing with the research data in previous studies. The total en bloc spondylectomy(TES) was simulated to remove the L3 vertebral body and adjacent intervertebral discs, and a personalized artificial vertebral body was designed based on the design principles of artificial vertebral body and was fixed to the adjacent lumbar segments using a posterior approach with a titanium alloy rod-screw system. The interior of the artificial vertebral body was designed as honeycomb structures with densities of 30%, 50%, and 70%. PEEK/hydroxylaptite(HA) composite materials were selected as the external shell of the personalized lumbar artificial vertebral body, and PEEK/carbon fiber(CF) materials were used as the internal filler. The forces and moments of each vertebral body in the upright, forward bending, backward extension, lateral bending and rotation states were obtained through the Vicon Nexus system, and as the boundary conditions of finite element analysis, the appropriate size of the bone graft hole and the thickness of the shell were selected, and then the inside of the artificial vertebral body was filled with hexagonal honeycombs of different densities. The models of young and middle-aged and elderly groups were established by changing the elastic modulus of cortical bone and cancellous bone, and the finite element simulation was carried out on the models. The maximum stress values of the artificial vertebral body, fixation system and adjacent upper and lower endplates under different motion states, and the stress occlusion rate of the artificial vertebral body were analyzed to evaluate the performance of the artificial vertebral body. Results: The maximum stress value of artificial vertebral body(42.25MPa) was lower than the yield strength of PEEK/HA(65MPa), and the maximum stress value of internal honeycomb(26.38MPa) was lower than the yield strength of PEEK/CF(90MPa); The maximum stress value of rod-screw system (271.75MPa) was lower than the yield strength of titanium alloy(900MPa), and the maximum stress value of the endplate on adjacent endplate(7.87MPa) was lower than the yield strength of cartilage endplate(50MPa). The stress occlusion rate of artificial vertebral body with 30% honeycomb density in the middle-aged and elderly group was the lowest. Conclusions: The 3D-printed personalized artificial vertebral body of PEEK matrix composite can complete the structure reconstruction of lumbar spine well after TES with good biomechanical stability.