Assessment of mechanical and biological properties of Ti–31Nb–7.7Zr alloy for spinal surgery implant

Abstract In the development of spinal implants, the properties of materials play a very important role in the function of the implant. This study evaluates the mechanical properties and biocompatibility of Ti–31Nb–7.7Zr alloy compared to the widely used Ti–6Al–4V alloy for spinal implants. Mechanical properties and biocompatibility were tested by manufacturing commercially available screws and rods using Ti–31Nb–7.7Zr alloy. Static compression bending test, static torsion test, and static four-point bending test were performed using a mechanical testing machine in accordance with ASTM F1717-18 standard and ASTM F382-17 standard. Additionally, screw insertion torque analysis was measured through a cadaver experiment, and histologic analysis was performed through animal experiments using a rabbit. It demonstrates that Ti–31Nb–7.7Zr, with its high yield strength and low Young’s modulus, closely matches human bone’s elasticity, potentially reducing stress shielding effects. Mechanical testing shows Ti–31Nb–7.7Zr’s superior performance in static compression, torsion, and bending tests. Biocompatibility assessments in vivo reveal no significant difference between the two materials, suggesting Ti–31Nb–7.7Zr’s suitability for spinal surgery applications. This research supports Ti–31Nb–7.7Zr alloy as a promising candidate for spinal implants, offering improved mechanical compatibility with bone and excellent biocompatibility.