Abstract
The intervertebral discs (IVD) are fibrocartilages tissues linking the vertebrae of thespine allowing its mobility as well as its stability. The low vascularity of this tissue can bethe root of the discs’ degeration which, when symptomatic, car lead to a herniated discor neurological pain. When the conservative treatment failed, the remaining solution is thesurgery. The surgery is a discectomy followed by a fusion or an arthroplasty (artificial discreplacement). The spinal fusion reduces the mobility while the implant retains it but withoutproviding the non-linear behavior or the natural disc or the shock absorbing properties. Inthis context, this work aims to study the properties of microstructures based on the Triply-Periodic Minimal Surfaces (TPMS) to mime the behavior of the human cervical disc for thepurpose of make a implant by stereolithography.The material used, developped by Thomas Brossier during his PhD carried out in parallelof this work, a hybrid copolymer composed of gelatin and poly(trimethylene carbonate)(PTMC), was tested in terms of biocompatibility. The influences of the stereolithographyprinting parameters (layer thickness, irradiation duration, laser power...) was also explored.Our work consisted in, first evaluate the mechanical properties of theses polymers accordingto the ratio of PTMC and gelatin.Then, the effectives rigidity tensors, of the TPMS microstructures, were calculated basedof the results of the periodic double-scale asymptotic expansion homogenization. In out case,the microstructure cell is periodic, initially cubic. Then, we explored the modification of classmaterials and the values of the effectif rigidity tensor by varying the dimensions of the cell(keeping a parallelepipedal cell) and the volume fraction.To view the influence of these parameters on the behavior of the microstructure, Youngmodulus surfaces were plotted. This allows to represent explicitally the anisotropy of thesesstructures and to identify the rigidity principal angles.The study of the Young modulus surfaces allows to highlight the influence of the volumefraction as well as the shape of the cell on the shape of the Young modulus surfaces. Forexample, if the structure is isotropic the surface is a perfect sphere. Based on theses results,it is possible to determine which of the five TPMS studied car mimic the anisotropic elasticbehavior of the humain cervical IVD. Theses results are not limited by a IVD applicationand can be applied to other tissue engineering application or even to the filling of orthopedicimplant.