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

Abstract

The rising prevalence of orthopedic conditions in aging populations has created a growing demand for advanced implants with enhanced biocompatibility, mechanical performance, and tissue integration. To meet these demands, it is necessary to investigate the metamaterial properties of cross-scale porous structures, including both macroscale architecture and microscale texture. Accordingly, we employed parametric modeling to design porous structures; analyzed blood flow distribution through various multi-level porous designs using mold flow simulation; evaluated their compressive properties through finite element analysis; assessed biocompatibility via animal experiments; and obtained tissue ingrowth data using micro-computed tomography. The results indicated that when fluid flowed through cross-scale porous structures, the overall pressure was low, and the Kelvin cell structure exhibited favorable flow field characteristics under low pressure. When the structures were pressurized, texturization methods involving material removal resulted in larger displacements, while those involving material addition led to smaller displacements. The Kelvin cell structure exhibited extensive tissue ingrowth with a dense tissue pattern internally, and the amount of ingrowth decreased from the inside to the outside. Increasing the roughness of porous structures via material removal increased the surface-to-volume ratio to a certain extent but did not promote tissue ingrowth. In contrast, increasing roughness by material addition favored tissue ingrowth, laying a foundation for the design of cross-scale metamaterial implants.

Keywords

3D printing / Biocompatibility / Mechanical properties / Metamaterial / Porous structure

Funding

The study was funded by the National Natural Science Foundation of China (grant no. 52575470), Natural Science Foundation Project of Henan Province (grant no. 252300421971) and the Zhoukou Science and Technology Plan Project (grant no. ZKSKJGG 100084).

Conflict of Interest

The authors declare no conflicts of interest.

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