Prospects of low-modulus alloys of the Ti-(15-20)Nb-(5-10)Ta system for engineering implants used in traumatology and orthopedics. A preclinical study

Aim Study of mechanical and biological properties of five variants of alloys of the Ti-Nb-Ta system. Materials and methods Five alloys were obtained from the system: Ti-(15-20)Nb-(5-10)Ta (at. %). Their mechanical tests were carried out by stretching on the INSTRON 3382 universal testing machine in accordance with GOST 1497-84. The biological properties of the resulting alloys were evaluated in in vivo experiments (implantation surgery) on white outbred male JCR mice. Histological study of the tissues of the limb with an implant, kidneys and liver was carried out at three time points: at 1, 4, 12 weeks after surgery, which corresponds to the early, middle and late phases after implantation. Results The samples showed ductility from 11.5 % to 14.6 %, strength from 549 to 673 MPa and Young's modulus from 42 to 50 GPa. The yield strength also varied depending on the composition of the alloy within 188 - 572 MPa. The inflammatory reaction was the least pronounced in the groups with Ti-20Nb-5Ta and Ti-15Nb-10Ta alloys implanted. Discussion Compared to the widely used TiAl6V4 alloy, the obtained alloys approximately correspond in terms of plasticity and have approximately 2 times lower Young's modulus, which should lead to better biomechanical compatibility between the implant and the surrounding biological tissues, preventing the effect of protection against stress and, accordingly, bone resorption. The relatively low tensile strength of the obtained alloys does not reduce the above-mentioned advantage over TiAl6V4, since this strength is quite sufficient for the proposed application. Histological study after 1, 4 and 12 weeks showed that the intensity of the local inflammatory reaction due to new alloys is higher than with the use of TiAl6V4, which requires further study and could be associated with a small sample size. Conclusions The way to create titanium alloys with a low Young's modulus may solve the problem of biomechanical compatibility of the implant with the surrounding tissues. The obtained and described alloys of the Ti-Nb-Ta system showed the neceary mechanical and, according to the initial assessment, acceptable biological properties that require further broader research.