Graded cellular structures for enhanced performance of additively manufactured orthopaedic implants

Hip implants face a significant challenge due to their limited lifespan, a concern amplified by the rising human life expectancy. Lattice structures have demonstrated the ability to provide precise control over geometry, thereby significantly enhancing implant performance. This paper introduces the development of graded additively manufactured Ti6Al4V lattice structures for orthopaedic implants. The objective focuses on developing a graded lattice unit cell design mirroring human bone properties, emphasising high surface curvature and design versatility to improve mechanical and biomedical properties, specifically osseointegration and stress shielding. The study involves modelling and grading simple cubic (SC) and body-centred cubic (BCC) lattice structures with various geometries and graded conditions and conducting compressive tests to identify the optimal configuration. The results showed that filleting was found to be the mechanical strength. On the other hand, BCC lattice structures demonstrated superior performance compared to SC structures. The optimised structure with a pore size of 400 µm provided an elastic modulus of 15.7 GPa, yield strength of 296 MPa and compressive strength of 530 MPa. This graded lattice design approach provides a promising technique for enhancing hip implant performance, offering potential improvements.