According to the researchers, most prosthetics in use
today were developed over a decade ago and have no motor control. The
researchers will present the findings they have made in improving the
function of prosthetic hands and possibly restore the sense of touch
for injured patients at the 95th annual Clinical Congress of the
American College of Surgeons.
The project is being funded by
the Department of Defense and came from the need for improved
prosthetic devices to improve the life of soldiers wounded in battle.
Robotic prosthetics are already available for some uses and the goal
of the researchers was to overcome the shortcomings in today's
robotic devices. Namely, these shortcomings are the limited motor
control and no sensory feedback.
"Most of these
individuals are typically using a prosthesis design that was
developed decades ago," says Paul S. Cederna, M.D., a plastic
and reconstructive surgeon at U-M Health System and associate
professor of surgery at the U-M Medical School. "This effort is
to make a prosthesis that moves like a normal hand. There is a huge
need for a better nerve interface to control the upper extremity
The team of researchers created what they
call an artificial
neuromuscular junction that is made of muscle cells and a
nano-sized polymer placed on a biological scaffold. The body has
natural neuromuscular junctions, which are the point where nerves
innervate muscle to form connections from the brain to the
The bioengineered scaffold was placed over the severed
nerve endings like a sleeve. The researchers found that the muscle
cells on the scaffold were able to bond to the body's native nerve
sprouts and feed electrical impulses to the brain. The researchers
are testing on lab rats right now. In animals, the researchers were
able to get the scaffold to relay both motor and sensory electrical
impulses and create a target for the nerve endings to grow. It is
common for the body to grow an abnormal mass of nerve fibers at a
point where they are cut.
"The polymer has the ability to
pick up signals coming out of the nerve, and the nerve does not grow
an abnormal mass of nerve fibers," explains Cederna.
lab tests, rats were able to respond to the tickling of their feet
with the appropriate signals to move the limb according to the
researchers. If successful, the researchers will one-day move onto
human trials and may be able to give those missing limbs back sensory
input and mobility lost to accident and war.