Porous NiTi alloys combine benefits from shape memory effects and porous structure. These features make NiTi foams optimal candidates for orthopedic implant applications.
In particular, these materials display the following unique characteristics ([R1-2-3]):
- Good biocompatibility, compared to conventional implant materials (e.g. Ti);
- High strength, important to prevent deformation or fracture;
- Relatively low stiffness, useful to minimize stress shielding phenomenon;
- Shape recovery effect, that facilitates implant insertion and ensures good mechanical stability within the host tissue (moreover, a high recovery strain is useful to enhance bone growth);
- Good resistance to corrosion;
- Elevated osteoconductivity, due to its porosity, which enhances bone ingrowth and fluids transportation (this characteristic makes porous NiTi a bioactive material);
- Better osseointegration than titanium;
- Better osseointegration and osteoconductivity than bulk NiTi alloys;
- Excellent compatibility with magnetic resonance imaging and computer tomography scanning.
Research on porous NiTi is still required in order to successfully exploit this material in orthopedics. Our research group is collaborating with the Chemistry Department of University of Pavia and with the Chemistry and Industrial Chemistry Department of University of Genova with the aim of manufacturing, modeling and testing porous Nitinol.
Fig. 1: Porous NiTi device for lumbar fusion (Actipore by Biorthex, Canada).
- [R1] Bansiddhi A., Sargeant T. D., Stupp S. I., Dunand D. C., 2008, “Porous NiTi for bone implants: A review”, Acta Biomaterialia 4 (2008) 773–782.
- [R2] Likibi F., Assad M., Coillard C., Chabot G., Rivard C. H., 2005, “Intégration et apposition osseuses des biomatériaux orthopédiques métalliques poreux et non poreux”, Annales de chirurgie 130 (2005) 235–241.
- [R3] Zhu S. L., Yang X. J., Fu D. H., Zhang L. Y., Li C. Y. and CY Z. D., 2005, “Stress-strain behavior of porous NiTi alloys prepared by powders sintering”, Mater Sci Eng A – Struct Mater Prop Microstruct Proc 408 (2005) 264–268.