3D printed porous Ti6Al4V cage: Effects of additive angle on surface properties and biocompatibility; bone ingrowth in Beagle tibia model

Abstract

Similar mechanical properties to native bone, excellent biocompatibility and osseointegration are key factors for interbody fusion cage. In the present study, porous Ti6Al4V cage with computer designed macro- and micro-architecture was reproduced by selective laser melting (SLM). Dense Ti6Al4V discs with six different angles were fabricated to investigate the effects of additive angle (inevitable in SLM manufacturing) on surface properties and biocompatibility. As angle increased, both surface roughness and hydrophobicity increased due to increases in the number of unmelted metallic particles. In the early stage of cell culture, more elongated MC3T3E1 cells were observed at higher additive angle, but cell adhesion and proliferation with different angle did not show statistically differences. Bullet-shaped Ti6Al4V cage with opened window, porosity of 70% and pore size of 600 μm revealed elastic modulus of 0.51 ± 0.04 GPa and ultimate compressive strength of 94.7 MPa at 0.29% strain, which is comparable with the commercialized polyetheretherketone cage. In vivo evaluation of Beagle tibia model through histological analysis showed that the cylindrical porous body with same porosity and pore size achieved similar bone ingrowth as commercialized porous tantalum implant at 4 and 12 weeks, indicating SLM fabricated porous Ti6Al4V cage holds great potential for spinal fusion. Keywords: Selective laser melting, Additive angle, Interbody fusion cage, Mechanical properties, Biocompatibility, Bone ingrowth