Effective design and mechanical response of Gyroid lattice scaffold for orthopedic implants

Abstract

Compared to solid metallic implants, lattice (porous) Ti-6Al-4 V scaffolds provide better osteointegration and minimize the stress shielding effect by bringing down the effective elastic modulus of implants closer to the natural bones. According to available literature, the pore shape, pore size and surface curvature of lattice structures strongly influence implants' osteointegration capacity and mechanical integrity. Triply periodic minimal surface (TPMS) based Gyroid lattice structure has been widely studied by researchers for orthopedic implant applications. In this research, Gyroid unit cells were designed for orthopedic implant applications, considering optimum lattice design parameters like pore shape and curvature (TPMS skeletal Gyroid), pore size (800–1000 µm), porosity (70–85 % with a variation of 5 %) and manufacturing constraints for additive manufacturing (AM), to obtain reduced stiffness of implants, equivalent to bone and better osteointegration. The lattice structures were manufactured using direct metal laser sintering (DMLS), an additive manufacturing technology. The mechanical stability of lattice structures was analyzed using the finite element method and mechanical testing under compressive loads. The compression analysis results indicate that lattice structures with 70–85 % porosity impose stiffness and strength on par with the trabecular bone, thus helping reduce stress shielding. For implantation near the regions where cortical bones are prominent, stiffness and strength need to be improved. The micro defects generated during additive manufacturing potentially reduced the mechanical strength.