Structural geometries and mechanical properties of vertebral implant with honeycomb sandwich structure for vertebral compression fractures: a finite element analysis.BACKGROUND
 Because of osteoporosis, traffic accidents, falling from high places, and other reasons, the vertebral body can be compressed and even collapse.  Vertebral implants can be used for clinical treatment.  Because of the advantages of honeycomb sandwich structures, such as low cost, less material, light weight, high strength, and good cushioning performance.  In this paper, the honeycomb sandwich structure was used as the basic structure of vertebral implants.


 The orthogonal experiment method is applied to analyse the size effect of honeycomb sandwich structures by the finite element method.  Based on the minimum requirements of three indexes of peak stress, axial deformation, and anterior-posterior deformation, the optimal structure size was determined.  Furthermore, through local optimization of the overall structure of the implant, a better honeycomb sandwich structure vertebral implant was designed.


 The optimal structure size combination was determined as a panel thickness of 1 mm, wall thickness if 0.49 mm, cell side length of 1 mm, and height of 6 mm.  Through local optimization, the peak stress was further reduced, the overall stress distribution was uniform, and the deformation was reduced.  The optimized peak stress decreased to 1.041 MPa, the axial deformation was 0.1110%, and the anterior-posterior deformation was 0.0145%.  A vertebral implant with good mechanical performance was designed.


 CONCLUSIONS
 This paper is the first to investigate vertebral implants with honeycomb sandwich structures.  The design and analysis of the vertebral implant with a honeycomb sandwich structure were processed by the finite element method.  This research can provide a feasible way to analyse and design clinical implants based on biomechanical principles.
C