Bone-mimicking TPMS gyroid design for osteoporotic fracture fixation: analysis of structural efficiency with simulation study on 316L stainless steel

Abstract Fracture fixation devices for load-bearing bones are typically made from stainless steel, titanium, or cobalt-chromium alloys, but their high stiffness can cause stress shielding with detrimental effect on bone density, reducing implant anchorage, leading to implant loosening, particularly in osteoporotic bones. Low-elastic materials reduce stress shielding, but issues with implant anchorage in fixation of brittle bone cause persistent implant failures. Effective management of porous designs that promote bone ingrowth while maintaining structural efficiency is crucial in these cases. This study addresses the issue by proposing gyroid-based lattice designs that mimic cortical bone porosity (5–15%) for fracture fixation plates, aiming to reduce stress shielding and enhance bone ingrowth for improved anchorage. A three-stage Implicit Finite Element Analysis (FEA) was performed using Ansys. Static four-point bending simulations confirmed the design's suitability for 316L stainless steel in femur, tibia, and humerus fixation in accordance with United States Food and Drug Administration (US-FDA) criteria. Tensile simulations showed a reduction in Young’s modulus from 193 to 178 GPa, indicating an 8% reduction in elasticity. This shift moves closer to the elasticity of bone, representing progress in minimizing stress shielding effect while balancing strength. Biomechanical simulation with plate and bone interaction also demonstrated six-time increased stress flow to the bone with porous gyroid structured implant. In comparison, simple cubic lattice designs failed to meet US-FDA criteria, while the gyroid designs exhibited 25% higher mechanical properties. The gyroid design shows promise in improving bone stability, reducing stress shielding, and meeting US-FDA performance criteria in load-bearing fractures. Graphical abstract