Structure, metallurgy, and mechanical properties of a porous tantalum foam.

This study evaluated a porous tantalum biomaterial (Hedrocel) designed to function as a scaffold for osseous ingrowth. Samples were characterized for structure, Vickers microhardness, compressive cantilever bending, and tensile properties, as well as compressive and cantilever bending fatigue. The structure consisted of regularly arranged cells having struts with a vitreous carbon core with layers of CVI deposited crystalline tantalum. Microhardness values ranged from 240-393, compressive strength was 60 +/- 18 MPa, tensile strength was 63 +/- 6 MPa, and bending strength was 110 +/- 14 MPa. The compressive fatigue endurance limit was 23 MPa at 5 x 10(6) cycles with samples exhibiting significant plastic deformation. SEM examination showed cracking at strut junctions 45 degrees to the axis of the applied load. The cantilever bending fatigue endurance limit was 35 MPa at 5 x 10(6) cycles, and SEM examination showed failure due to cracking of the struts on the tension side of the sample. While properties were variable due to morphology, results indicate that the material provides structural support while bone ingrowth is occurring. These findings, coupled with the superior biocompatibility of tantalum, makes the material a candidate for a number of clinical applications and warrants further and continued laboratory and clinical investigation.