Fabrication of open-cellular (porous) titanium alloy implants: osseointegration, vascularization and preliminary human trials

In this study we describe the fabrication of a variety of open-cellular titanium alloy (Ti-6Al-4V) implants, both reticular mesh and foam structures, using electron beam melting (EBM). These structures allow for the elimination of stress shielding by adjusting the porosity (or density) to produce an elastic modulus (or stiffness) to match that of both soft (trabecular) and hard (cortical) bone, as well as allowing for bone cell ingrowth, increased cell density, and all-matrix interactions; the latter involving the interplay between bone morphogenetic protein (BMP-2) and osteoblast functions. The early formation and characterization of elementary vascular structures in an aqueous hydrogel matrix are illustrated. Preliminary results for both animal (sheep) and human trials for a number of EBM-fabricated, and often patient-specific Ti-alloy implants are also presented and summarized. The results, while preliminary, support the concept and development of successful, porous, engineered living implants.