Design and performance study of 3D-printed cross-scale metamaterial porous structures for orthopedic implants

To obtain bio-fixed implants with excellent performance, it is necessary to investigate the metamaterial properties of cross-scale (macroscale structure and microscale texture) porous structures. To this end, we employed parametric modeling to design porous structures; analyzed the flow field distribution of blood flowing through different multi-level porous structures using mold flow simulation; analyzed the compressive properties of porous structures using finite element simulation; assessed the biocompatibility of porous structures via animal experiments and acquired tissue ingrowth data within porous structures using Micro-CT. The results indicated that when fluid flowed through cross-scale porous structures, the overall pressure was low, the Kelvin Cell structure exhibited good flow field characteristics under low pressure. When the structure was pressurized, texturization methods involving material removal resulted in larger displacements, while those involving material addition resulted in smaller displacements. The Kelvin Cell structure exhibited extensive tissue ingrowth, with a dense tissue pattern inside, and the amount of ingrowth decreased from inside to outside; increasing the roughness of porous structures by material removal increased the surface-to-volume ratio to a certain extent, but did not favor tissue ingrowth, while increasing roughness by material addition favored tissue ingrowth, laying a foundation for the design of cross-scale metamaterial implants.