Fatigue performance of additively manufactured porous titanium for orthopaedic applications

Lattice structures are increasingly being adopted for orthopaedic implant designs; however, questions remain about the long-term strength and risk of fatigue failure of porous titanium (Ti) and Ti-alloy structures. To provide a deeper understanding of this issue, this study conducted a comprehensive review of fatigue performance of latticed Ti/Ti-alloy parts, printed via laser powder bed fusion (PBF-LB), for orthopaedic applications, spanning studies over the past decade. Key lattice parameters were collected, including porosity, pore size, feature thickness, and lattice type, and their corresponding effect on fatigue performance of the end part. This review found that many Ti/Ti-alloy lattice structures can achieve comparable mechanical properties to trabecular bone (E of 0.01-3 GPa, fatigue strength of 0.3-3 MPa) while only one reviewed sample matched both the Young's modulus and fatigue strength of cortical bone (E of 15-20 GPa, fatigue strength 40-60 MPa). This review addresses the gap in having consolidated data describing the effects of various properties of Ti/Ti-alloy lattices on their compressive fatigue strengths, providing guidance on design considerations of such lattice structures for orthopaedic applications. Data provided in this review further highlights the need for continued development of implant latticing strategies and design parameter development to better mimic human cortical bone in orthopaedic implants.