Characterization of additively manufactured SS316L lattice geometries for lumbar interbody fusion cage application

The Additive Manufacturing provides the capability of fabricate solid and hollow structures. Selective Laser Melting, an additive manufacturing technique, uses a powder bed and a laser melts the powder according to a trajectory needed to generate a 2D layer, then another layer of powder is distributed, and this layer is melted. This process is repeated, and the result is a 3D piece made of 2D layers. Hollow structures can be created reducing the material volume fraction and allowing to have desired mechanical properties for a specific behavior of a piece. For orthopedic implants, hollow pieces allow matching the mechanical properties of the implant to the ones of the surrounding tissue where it is pretended to be placed. Lattice structure are a kind of hollow structures used in many fields, including the health one. In this work, lattice structure cylinders with three different lattice structure (Body centered cubic, Body centered hexagonal and Tetrahedron) of two different unit cell sizes (3x3x3 and 6x6xx mm) with a strut diameter set as 800 µm were fabricated in SS316L using SLM technique and submitted to compression test to be characterized mechanically in order to know their mechanical behavior. Considering the Young’s modulus of the different arrangements, the Tetrahedron lattice structure with a unit cell size of 3x3x3 mm and the same strut diameter was selected to create a lumbar interbody fusion cage, and another unit cell size of 4x4x4 mm was proposed to study with this same geometry. These lumbar cages achieved a Young’s modulus near to the vertebrae cortical and trabecular bone, allowing the correct transmission of loads. For future work, it is proposed to replicate these experiments with Nitinol powder, a biocompatible and biomechanically compatible alloy.

https://orcid.org/0000-0003-2289-4239