Flexible yet rigid like a human bone, and immediately capable of bearing loads: A new kind of implant, made of titanium foam, resembles the inside of a bone in terms of its structural configuration. Not only does this make it less stiff than conventional massive implants. It also promotes ingrowth into surrounding bones.
Among implants, the titanium alloy Ti6Al4V is the material of choice. It is durable, stable, resilient, and well tolerated by the body. But it is somewhat difficult to manufacture: titanium reacts with oxygen, nitrogen and carbon at high temperatures, for example. This makes it brittle and breakable. The range of production processes is equally limited.
Titanium foam has a complex internal structure that allows blood vessels and existing bone cells to grow into the foam, integrating them into its own matrix (and vice versa). This makes the foam particularly useful to repair damaged bones that are still partially intact
For constructing bone replacements or prosthetics, the Titanium foam serves a slightly different function; it become more or less dense as the weight-bearing requirements of the substitute bone demand — meaning, for instance, that a fingertip bone doesn’t need to be as heavy per cubic inch as a femur.
Finally, titanium foam allows for stress to be replaced on the repaired bone immediately. In fact, it requires it: only load-bearing stress can trigger the proper density formation of the graft and integration of the existing bone with the foam, fostering faster and more substantive healing
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