A 60-70% porous reticulated titanium foam was developed using a repliform process to serve as a scaffold for bone ingrowth in load-bearing orthopedic applications.

Compressive and flexural properties were evaluated as a function of porosity. Bond strength to Ti-alloy substrates was evaluated. Abrasion and friction tests were conducted to compare the titanium foam to porous bead and plasma spray surfaces and morphological parameters were evaluated using image analysis. In vivo performance was studied in metaphyseal and diaphyseal canine models with implantation times of 3, 6, and 12 weeks. End points of the in vivo studies included quantitative histology and mechanical testing.

The mean interconnecting pore diameter was around 200µm, with pore cells approximately 530µm in diameter. The ultimate compressive and flexural strengths were dependent on porosity, with compressive strengths of 79-93 MPa at ~70% porosity and 141 MPa at 64% porosity. The compressive modulus ranged from 2.5 GPa to 3.8 GPa. Flexural strength of samples near 70% porosity was in excess of 100 MPa. Abrasion resistance of the porous titanium coating was found to be equivalent to that of bead coatings while exceeding the abrasion resistance of plasma spray coatings. The coefficient of friction was higher than that of porous bead coatings and equivalent to that of plasma spray coatings. Lap-shear and tensile pull-off tests of coated Ti6Al4V substrates resulted in strengths greater than 40 MPa. The canine studies showed rapid bone ingrowth and integration of the porous titanium specimens in both trabecular and cortical bone.

The extensive testing performed on this new porous titanium material has shown that it is suitable for orthopedic implant coatings and stand-alone implants.