Researchers
at the Fraunhofer Institute for Manufacturing and Advanced Materials
IFAM in Dresden have developed a new implant that has a structural
configuration just like the inside of a human bone, but is made out
of titanium
foam.
Dr.-Ing
Peter Quadbeck of the Fraunhofer Institute for Manufacturing and
Advanced Materials is lead developer of the "TiFoam"
project and has created a titanium foam implant that
is rigid and flexible like a real human bone. Most importantly, it
allows ingrowth into surrounding bones.
Other
massive bone implants have not worked in the past because they
contained characteristics that are different from the human skeleton,
such as stiffness. Massive bone implants that are not flexible like
a real
human bone causes more stress to be put on the implant
instead of the adjacent bone, which, as a result, could lead to the
deterioration of that bone.
Bones
that are exposed to lesser strains normally have lesser bone density.
Stress on the bone "stimulates the growth of the matrix."
Also, the rigidity of real bones allows blood vessels and bone cells
to grow in the pores and channels this shape offers. So while these
stiff implants can be good for defects in load-bearing bones, they do
not promote ingrowth to surrounding bones because they are neither
flexible nor shaped rigidly like real bones.
The
secret behind the new titanium foam implants is a foam-like structure
that resembles spongiosa inside human bones, and a powder
metallurgy-based molding process that consists of open-cell
polyurethane (PU) foams being saturated with a solution that contains
a binding medium and a fine titanium powder. The powder adheres to
the foams cellular
structures, and the binding agents and the PU are vaporized. The
end result 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," said Quadbeck. "This
applies foremost to the balance between extreme durability and
minimal rigidity."
This
careful balance allows the forces of weight and motion to sustain,
the forces of stress to be transmitted, the formation of new bone
cells and healing of the implant. Doctors may be able to use this new
material to bond implants to patient's bones more efficiently and on
a more stable basis.
