Researchers at the Fraunhofer Institute for Manufacturing and Advanced Materials in Dresden have developed a titanium “foam” that may be a better material to use than solid titanium in orthopedic implants. Because of its porous structure, the researchers believe bone will better grow into the implant which itself will be lighter due to less material used.
The titanium foam is the result of a powder metallurgy-based molding process that has already proven its value 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. The powder cleaves to the cellular structures of the foams. The PU and binding agents are then vaporized. What remains is a semblance of the foam structures, which is ultimately sintered. "The mechanical properties of titanium foams made this way closely approach those of the human bone", reports Quadbeck [Dr. Peter Quadbeck of the Fraunhofer Institute for Manufacturing and Advanced Materials IFAM in Dresden]. "This applies foremost to the balance between extreme durability and minimal rigidity." The former is an important precondition for its use on bones, which have to sustain the forces of both weight and motion. Bone-like rigidity allows for stress forces to be transmitted; with the new formation of bone cells, it also fosters healing of the implant. Consequently, stress can and should be applied to the implant immediately after insertion.
In the "TiFoam" project, the research partners concentrated on demonstrating the viability of titanium foam for replacement of defective vertebral bodies. The foam is equally suitable for "repairing" other severely stressed bones. In addition to the materials scientists from the Fraunhofer institutes IFAM and IKTS – the Institute for Ceramic Technologies and Systems in Dresden – physicians from the medical center at the Technical University of Dresden and from several companies were involved in developing the titanium foam. Project partner InnoTERE already announced that it would soon develop and manufacture "TiFoam"-based bone implants.
Press release: Titanium foams replace injured bones…
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