What is stronger titanium alloy or bone

Titanium foams replace injured bones

People grow with their tasks. The same applies to his bones: if they are subjected to greater stress, denser tissue develops. Less stressed parts have a lower bone density. The stimulus of the load stimulates the growth of the matrix. In the future, doctors want to make greater use of this effect in order to connect implants to the patient's bones in a more permanent and stable manner. For this, the bone replacement must be designed in such a way that it favors ingrowth - with pores and channels through which blood vessels and bone cells can grow unhindered.

The material of choice for implants is titanium. It is durable, stable and resilient and is well tolerated by the body. Its processing is rather problematic: Titanium reacts with oxygen, nitrogen and carbon at high temperatures. It becomes brittle and fragile.

Complex internal structures cannot yet be produced using the established processes. That is why massive titanium implants are mainly used for defects in load-bearing bones. Many have textured surfaces to provide support for bone cells. But the connection remains fragile. In addition, massive implants have different mechanical properties: They are more rigid.

“The adjacent bone is hardly stressed and in the worst case it even recedes. The implant loosens and has to be replaced, ”explains Doctor Peter Quadbeck from the Fraunhofer Institute for Manufacturing Technology and Applied Materials Research IFAM in Dresden. Quadbeck coordinates the "TiFoam" project, in which a titanium material for new implants was created. In its foam-like structure, the material resembles the cancellous bone inside the bone.

The titanium foam is created using a powder-metallurgical molding process: Open-cell foams made of polyurethane (PU) are impregnated with a solution of binding agent and fine titanium powder. The powder is deposited on the cell structures of the foams. PU and binder are evaporated. What remains is an image of the foam structure, which is finally sintered. "The mechanical properties of the titanium foams produced in this way come very close to those of human bone," reports Quadbeck. "This mainly applies to the balance between high strength and low rigidity."

The former is an important requirement for use in bones that need to withstand weight and movement. A bone-like stiffness transmits stress stimuli and promotes the healing of the implant with the formation of new bone cells. This can and should therefore be loaded immediately after insertion.

MEDICA.de; Source: Fraunhofer Society