Messenger - Vol. 4, No. 1, Page 5
UD researcher has a bone-ified first

     To a person whose life has been diminished by the pain of an
arthritic hip, a bone implant can be a miracle. But, the miracle is
often short-lived because as many as 15 percent of the implants
performed each year are rejected by the body within five years.
     Suresh Advani, professor of mechanical engineering at the
University of Delaware, says he believes an implant made of short
fiber composites (SFC) would better "mimic the response of the bone in
the body" than titanium, one of the alloys now used for implants.
     Advani says the 150,000 hip implants performed each year are
supposed to provide relief from pain for at least 20 years, but about
22,000 fail between five and seven years after the implant. He blames
the inflexibility of the advanced aerospace alloys used to make the
     The cobalt-, chromium- or titanium-based alloys, developed for
high-performance jet engines, are used in the body because they won't
corrode or break down during the 20-year life expectancy of an
     The problem is that these materials are rigid. They don't
distribute the normal stress load on the bone evenly, Advani says. At
points where the implant is less flexible than the bone, the lack of
stimulation on the bone causes it to lose density and move away from
the implant.
     Advani and a student, Sunil Gupte, have shown through a computer
model that the short fiber implant, more like the bone itself in
composition, meshes with the bone, distributing the stress load
equally. This keeps the bone from losing density and pulling away from
the pin.
     Advani says his work on short fiber composite implants is a
first. Until his research, everyone believed SFCs would have shattered
under the extreme impact needed to install a pin.
     "With improvements in the fiber and matrix material properties
and manufacturing technique over the years, I believe it can withstand
the impact now," Advani says.
     If SFC implants become the material of choice, Advani's computer
model can be used to determine how best to manufacture at the lowest
cost and to create the best match for each recipient. "People's bodies
are different. If an implant for someone heavy could be made more
stiff or, for someone lighter, more flexible, the implant would be
closer to the real thing," Advani says.
     Until there is a prototype, Advani has only his computer model to
verify his conclusions. He has asked the University's senior design
students to take on the production of a prototype as one of their
projects, and colleagues at the Imperial College in London have begun
working on one.
     Dr. Freeman Miller, a physician with the A.I. duPont Institute in
Wilmington, Del., has agreed to test the prototype implant in the bone
of a pig.
     Advani says the growing need for successful bone implants makes
composites inevitable. "My feeling is it is going to happen. It's just
a matter of time."
                                                     -Barbara Garrison