Structural design and mechanical performance evaluation of personalized irregular porous L3-L4 fusion cage by additive manufacturing.

With the advent of additive manufacturing, it has become feasible to fabricate personalized porous fusion cages for biomedical applications. This study aims to ensure a suitable range of pore sizes for bone tissue and cell growth, investigate the biomechanical properties of irregular porous fusion cages at different target pore sizes, determine optimal structural parameters, and evaluate their mechanical properties. In this study, TC4 irregular porous fusion cages with varying target apertures were designed using the Voronoi method for the L3-L4 intervertebral space of the lumbar spine. Finite element simulations of the entire lumbar spine model were performed under both upright and torsional working conditions. Biomechanical properties were evaluated to determine the optimal structural fusion cage. Optimal parametric structural samples were fabricated by SLM and their mechanical properties were determined by compression and tensile tests. The results show that the fully porous fusion cage with a target pore size of 0.6 mm is relatively stable under the above two operating conditions and is not prone to collapse, which reduces the risk of stress shielding. At the same time, the compression yield strength and elastic modulus are 153.78 MPa and 5.82 GPa, respectively, and the tensile ultimate load reaches 5000N. The mechanical properties are similar to those of bone tissue and meet human performance requirements.