Optimising geometrical features of additively manufactured lattice structures for improved mechanical performance of interbody cages

Despite the widespread use of lattice structures in spinal surgery, the specific influence of unit-cell microgeometrical features on the mechanical stability of interbody cages remains underexplored. This study evaluates the impact of geometric modifications on the mechanical properties of Ti6Al4V lattice structures fabricated via Laser Powder Bed Fusion (LPBF) for interbody cage implants, with a specific focus on the basic cell architecture. The evaluation of eight lattice geometries, based on geometric modifications of the combination of two hexagonal pyramids characterized by three parameters: H – cell height, W – width of the arm spacing base vertices, h − height of the connection point between arms. The mechanical properties of the individual lattice variants were determined through uniaxial compression loading tests conducted through both experimental and numerical studies. Our research indicates that even minor modifications to the geometry of the basic cell have a significant impact on the mechanical properties of lattice structures. The connector height (h) was identified as the most influential parameter, governing stiffness and load-bearing capacity, and affecting stress distribution. With 16–26% porosity and pore sizes of 800–1010 µm, lattice structures were designed to promote bone ingrowth and osseointegration without compromising the implant’s structural strength.