A female Swedish patient with
hand amputation has become the first recipient of an osseo-neuromuscular
implant to control a dexterous hand prosthesis. In a pioneering surgery,
titanium implants were placed in the two forearm bones (radius and ulnar), from
which electrodes to nerves and muscle were extended to extract signals to
control a robotic hand and to provide tactile sensations. This makes it the
first clinically viable, dexterous and sentient prosthetic hand usable in real
life. Conventional prosthetic hands rely on electrodes placed over the skin to
extract control signals from the underlying stump muscles. These superficial
electrodes deliver limited and unreliable signals that only allow control of a
couple of gross movements (opening and closing the hand). Richer and more
reliable information can be obtained by implanting electrodes in all remaining
muscle in the stump instead. Sixteen electrodes were implanted in this first patient
in order to achieve more dexterous control of a novel prosthetic hand developed
in Italy by the Scuola Superiore Sant'Anna and Prensilia.
Current prosthetic hands have
also limited sensory feedback. They do not provide tactile or kinesthetic sensation,
so the user can only rely on vision while using the prosthesis. Users cannot
tell how strongly an object is grasped, or even when contact has been made. By
implanting electrodes in the nerves that used to be connected to the lost
biological sensors of the hand, researchers can electrically stimulate these
nerves in a similar manner as information conveyed by the biological hand. This
results in the patient perceiving sensations originating in the new prosthetic
hand, as it is equipped with sensors that drive the stimulation of the nerve to
deliver such sensations. One of the most important aspects of this work is that
this is the first technology usable in daily life. This means it is not limited
to a research laboratory. The patient is following a rehabilitation program to
regain the strength in her forearm bones to be able to fully load the
prosthetic hand. In parallel, she is also relearning how to control her missing
hand using virtual reality, and in few weeks, she will be using a prosthetic
hand with increasing function and sensations in her daily life.
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