Abstract
Additive manufacturing is rapidly becoming a key technology within commercial biomedical applications. Due to the advancements in the last two decades, additive manufacturing is a viable option for manufacturing complex structures that cannot be achieved with traditional manufacturing methods. One area of additive manufacturing that has received significant attention are porous biomaterials. Porous biomaterials, or scaffolds, provide a structure made up of a network of pores into which tissue can grow and regenerate. These scaffold structures are commonly applied as a biomaterial for orthopaedic applications. One such application is spinal fusion devices. When combined with a biocompatible material such as titanium, osteogenic cells can adhere to the surface of the scaffold, while the network of pores provide space for vascularisation, bone ingrowth and nutrient supply. Despite the previously undertaken research, there are research gaps for investigating unique structures with tailorable mechanical properties that can provide the ideal mechanical environment for osseointegration.
In this work the properties of a Ti-6Al-4V dodecahedron unit scaffold structure, additively manufactured using direct metal printing (DMP), were characterised to understand how these properties vary with alteration to the geometry. Both computational and mechanical testing methods were used to validate the mechanical properties. It was found that the dodecahedron scaffold structure was a tough material with favourable elastic properties and excellent post-yield properties. The relationships for these properties were converted into an optimisation process where the optimal scaffold design can be chosen based on design constraints.
It is known that mechanical stimulus is a significant factor in regard to bone growth. Therefore, a finite element (FE) model of the lumbar region of the spine implanted with a spinal fusion device (SFD) was developed. This model was used to provide insight into the biophysical stimulus within the scaffold region that would be responsible for promoting bone formation. The computational spine model demonstrated that a four screw integrated SFD configuration was superior to a three screw integrated configuration with respect to stability and had a lower risk of causing failure within the vertebral bodies. Furthermore, FE modelling of SFD designs showed that optimised dodecahedral scaffold architectures with elastic moduli values between 0.25GPa and 1.5GPa resulted in strain magnitudes and distributions within well-established strain ranges that were predicted to lead to enhanced bone formation.