When is a bone not made of bone? When it’s an implant. And we’ve been replacing bones with implants for a good while now. One of the best materials that we’ve found so far for this is titanium, an incredible strong metal that, luckily for us, the human body doesn’t tend to reject the presence of.
But titanium bone implants still have a few problems, and that has to do with the nature of titanium, and the nature of bone. You see like many things in the human body, bone density comes from the use of the bone itself. The constant pressures we exert on our bones force the body to toughen the bone up, making it denser. Reduce or eliminate that pressure entirely and the body will in turn reduce the density of the bone. This is why astronauts in zero gravity for extended periods of time risk losing bone density. Without the rigors of gravity constantly bearing down on them, their bones will start to adjust to the lowered demands upon them.
What does this have to do with bone implants? Everything. When you replace the somewhat flexible real bone with an implant made of extremely strong and rigid titanium, the titanium refuses to flex. It ends up taking more of the workload of the bones around it, reducing the pressure on them. And what happens when bones are relieved of everyday stresses? They lose density. They become weaker. And as they become weaker not only are they more prone to becoming damaged themselves, but the bond that they have to the titanium implant can break.
So titanium implants aren’t a perfect solution. But they’re the best that we have.
Enter materials scientists from the Fraunhofer institutes IFAM and IKTS, the Institute for Ceramic Technologies and Systems in Dresden, and physicians from the medical center at the Technological University of Dresden, as well as members of several additional companies such as project partner InnoTERE. And what have they come up with? TiFoam.
TiFoam, titanium foam, is still made of titanium alloy like ordinary titanium bone replacement implants, but the structure is something completely different. Instead of a single solid rigid piece of titanium, TiFoam is a flexible but strong foam-like structure made of titanium, mimicking the spongiosa found inside of real bones.
TiFoam is produced by creating an open-cell polyurethane (PU) foam structure how you want the final product to resemble. Then you saturate it with a solution of binding medium and a fine titanium powder. Once the titanium powder has adhered to the structure via the binding medium, you vaporize the actual foam and the binding agent with it. What you’re left with is just the titanium, still in the shape of the foam structure, solidified and ready to go.
Because TiFoam is more flexible than a solid hunk of titanium it allows the body’s normal transference of stress to the real bones around it, keeping them dense and strong. Also, because the titanium foam is hollow, it allows bone to grow in around it, called ingrowth, better strengthening its connection to the real bones. Further yet, TiFoam’s hollow nature also allows the ingrowth of blood vessels as well, making for healthier bone and tissue around the implant.
All of this amounts to a healthier body around the implant, a strong connection to the implant that is unlikely to break over time, and a faster healing process immediately after the surgery in which stress not only can be put upon the implant sooner after surgery, but should be applied to the implant after surgery to foster ingrowth and a stronger connection to the body.
TiFoam is just plain better as a bone replacement than traditional titanium implants.
And how soon will it be coming to market then? While exact dates seem to still be up in the air as this is new research, InnoTERE has already announced that it intends to develop and manufacture bone implants based on the TiFoam technology.