For an amputee, replacing a missing limb with a functional
prosthetic can alleviate physical or emotional distress and mean a return of
vocational ability or cosmetics.
Studies show, however, that up to 50% of hand amputees still
do not use their prosthesis regularly due to less than ideal functionality,
appearance, and controllability. But Silvestro Micera, of the École
Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, is paving the way for
new, smart prosthetics that connect directly to the nervous system. The
benefits are more versatile prosthetics with intuitive motor control and
realistic sensory feedback—in essence, they could one day return dexterity and
the sensation of touch to an amputee.
At the 2013 Annual Meeting of the American Association for
the Advancement of Science (AAAS) in Boston, Micera reports the results of
previous work conducting a four-week clinical trial that improved sensory
feedback in amputees by using intraneural electrodes implanted into the median
and ulnar nerves.
This interface holds great promise because of its ability to
create an intimate and natural connection with the nerves, and because it is
less invasive than other methods. It also provides fast, intuitive,
bidirectional flow of information between the nervous system and the
prosthetic, resulting in a more realistic experience and ultimately improved
"We could be on the cusp of providing new and more
effective clinical solutions to amputees in the next years," says Micera,
who is Head of the Translational Neural Engineering Laboratory at EPFL and
Professor at the Scuola Superiore Sant'Anna in Italy. Micera and colleagues
tested their system by implanting intraneural electrodes into the nerves of an
amputee. The electrodes stimulated the sensory peripheral system, delivering
different types of touch feelings.
Then the researchers analysed the motor neural signals
recorded from the nerves and showed that information related to grasping could
indeed be extracted. That information was then used to control a hand
prosthesis placed near the subject but not physically attached to the arm of
At AAAS in Boston, Micera also describes his recent
activities to improve the efficacy of this approach and announces a new
clinical trial starting soon as part of the Italian Ministry of Health's
NEMESIS project, under the clinical supervision of Prof. Paolo M. Rossini. This
new trial carries this research a step further by connecting the prosthetic
hand directly to the patient for the first real-time, bidirectional control
using peripheral neural signals. Though results are not yet available, the
researchers hope to find still further improvement in the sensory feedback and
overall control of the prosthetics with this new method.