A New Material for Implants: Titanium Foam

Porous titanium foam may be a better material to use than solid titanium in orthopedic implants, since bone could grow into the implant itself.

Researchers at the Fraunhofer Institute for Manufacturing and Advanced Materials (IFAM; Dresden, Germany) developed the new titanium material, which is the result of a powder metallurgy-based molding process used in the industrial production of ceramic filters for aluminum casting. Open-cell polyurethane (PU) foams are saturated with a solution consisting of a binding medium and a fine titanium powder. After the powder cleaves to the cellular structures of the foams, the PU and binding agents are vaporized. What remains is a semblance of the foam structures, which is ultimately sintered.


The resulting titanium foam resembles the spongiosa structure of bone, in terms of structural configuration; it is also flexible yet rigid, again like a human bone, and immediately capable of bearing loads, despite being lighter than regular titanium implants due to less material used, which also makes it less stiff than conventional massive implants. The foam-like structure also promotes ingrowth from the surrounding bones, making it equally suitable for repairing other severely stressed bones.

"The mechanical properties of titanium foams made this way closely approach those of the human bone,” said researcher Peter Quadbeck, Ph.D. "This applies foremost to the balance between extreme durability and minimal rigidity.”

Titanium is non-toxic even in large doses, and does not play any natural role inside the human body; however, it does have the inherent property to osseointegrate. As a result, skeletal loads are more evenly shared between bone and implant, leading to a lower incidence of bone degradation due to stress shielding and periprosthetic bone fractures, which occur at the boundaries of orthopedic implants. However, titanium alloys' stiffness is still more than twice that of bone, eventually leading to joint degradation. An estimated 0.8 milligrams of titanium is ingested by humans each day, but most passes through without being absorbed, despite a tendency to bioaccumulate in tissues that contain silica.

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Fraunhofer Institute for Manufacturing and Advanced Materials