Design and mechanical characterization of TPMS cellular structures additively manufactured by the selective laser melting process for use in intervertebral lumbar cages

Abstract

Cellular structures can reduce the stiffness of Ti-6Al-4 V and prevent the stress shielding effect. This research aimed to design and mechanically characterize triply periodic minimal surface (TPMS) cellular structures for use in intervertebral lumbar cages. To identify the appropriate structure and porosity, sheet-based gyroid, diamond, and Schwarz lattice structures were designed with different porosity levels from 45 to 80% and pore size of 720 µm. The behavior of porous samples was simulated under uniaxial compression using finite element simulation to predict the elastic modulus. The structures were also built using the metal additive manufacturing method, and then their elastic modulus was obtained by the uniaxial compression test. The simulation results and experimental tests differed by less than 10%, which was acceptable. The results indicated that the gyroid and diamond structures with 70 and 75% porosity had an elastic modulus (about 9 to 16 GPa) close to the elastic modulus of bone (7 to 20 GPa). Also, due to the high surface-to-volume ratio (about 7 to 16), these cellular structures were used in the cage design. Furthermore, the behavior of designed cages was also simulated in compression, compression-shear, and torsion. The simulation results indicated that the stress field created in the cellular structure of cages was much lower than the yield strength of the material. Therefore, the study concluded that the designed cages prevented the stress shielding effect and showed an acceptable mechanical behavior. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.