Low elastic modulus metals for joint prosthesis: Tantalum and nickel-titanium foams

In order to allow the ingrowth of the living tissue and increase the mechanical anchorage of the implant, Ta and NiTi foams were obtained with similar microstructure to cancellous bone and mechanically characterized. The Ta foams were produced by chemical vapour deposition and the NiTi foams by self-propagating high temperature synthesis (SHS). The mechanical and microestructural characterization was developed using a servohydraulic testing machine and microscopy techniques. In both materials, pores in an appropriate range of sizes and interconnectivity were observed, comparable with the nature bone morphology. Moreover, the foams showed an excellent biomechanical compatibility and compressive fatigue limit. The fatigue endurance limit set at 10⁸ cycles showed an approximate endurance limit of 7.5 and 13.2 MPa, for the NiTi and Ta foams, respectively. These results indicate that the studied materials provide an adequate structural support, showing mechanical properties similar to the cancellous bone, especially for the Ta foam.