Bioinspired Gradient Porous Hip Implant Design to Prevent Stress Shielding Using Stress Mapping and Bone Remodeling Theory

Abstract
Total Hip Arthroplasty (THA) is a widely performed surgical procedure, with increasing frequency worldwide. Despite its high success rate, many patients require revision surgeries due to complications such as aseptic loosening, primarily resulting from stress shielding, cortical hypertrophy, and micromotion. These issues often stem from a mechanical mismatch between the bone and the solid dense implant, particularly a mismatch in stiffness. A potential solution lies in the use of porous or lattice structures in implant design, which offer lower stiffness and improved biocompatibility by facilitating bone ingrowth, cell seeding, and vascularization. Among these designs, Triply Periodic Minimal Surfaces (TPMS), especially gyroid structures, closely resemble bone morphology and present a viable alternative to solid implants. However, optimizing parameters such as pore size, porosity, and wall thickness is critical for both biological integration and manufacturability. Given the nonuniform stress distribution experienced by implants under physiological loading, a gradient porosity design is necessary. This study develops a bio-inspired gyroid hip implant with gradient porosity, guided by stress mapping, and evaluates its impact on stress shielding in the femur through bone remodeling theory using finite element modeling (FEM). Results indicate that the gradient porous implant reduces stress shielding by 36.5% and can withstand mechanical loads with an acceptable safety factor.