Dual-graded lattice with mechanical bionics to enhance fatigue performance

Additive manufacturing (AM) is revolutionizing the design and fabrication of orthopedic implants, enabling the creation of complex graded structures to enhance biomechanical bionics. This study aims to enhance fatigue life and reduce stress shielding for a long-term stability by using functionally graded lattice. Various lattice with minimal surface, including uniform array, Z-axis graded, and dual-graded Gyroid, were designed and fabricated by selective laser melting (SLM), followed by mechanical and fatigue tests for validation of design objectives. With a novel Sigmoid-Boltzmann fusion algorithm, the dual-graded lattice enhances the artificial vertebral body (AVB) with an 11% increase in strength, >200% improvement in fatigue life and reduced stress shielding on the contact surface, benefiting long-term implant stability and biomechanical fidelity. It displayed outstanding resistance to fatigue crack propagation due to superior load-bearing capacity and energy absorption capabilities contributed by the graded central region. The findings highlight the significance of biomimetic design principles and offer insights into the optimization of orthopedic implants using dual-graded lattice.