Prosthetic Arm Moves Like A Real Limb

A new technique called targeted muscle reinnervation allows a neuro-controlled prosthetic arm to move as if it is a real limb, reports a new study.

Researchers at the Rehabilitation Institute of Chicago (RIC; IL, USA) have developed the new technique that offers improved control of a motorized prosthetic arm. They consequently conducted targeted reinnervation surgery on a 24-year old woman with a left arm amputation at the humeral neck. The reinnervation procedure allowed the re-routed nerves to grow into the appropriated muscle and direct the signals that they used to send to the amputated arm to the robotic arm (via surface electrodes) instead. This gave the patient better functional movement in her arm, and she reported using her neuro-controlled prosthesis for many hours a day.

Furthermore, using targeted sensory reinnervation, the sensation nerves to the hand were re-routed to a patch of skin on the patient's chest, so that when the patient is touched on this skin, she feels that her hand is being touched. This should eventually let her 'feel' what she is touching with an artificial hand, as if she were touching it with her own hand.
The results were published in the February 3, 2007, issue of The Lancet.

"This patient and our other three patients represent early application of the targeted reinnervation technique. Whether the improved function is enough to keep these patients wearing their devices in years to come, or whether they adapt to their new control even better and show greater functional gains, remains to be seen,” said Todd Kuiken, M.D., Ph.D., of the neural engineering center for artificial limbs, and colleagues. "Long-term follow-up is also needed to see how our patient's transfer sensation evolves.”

Targeted muscle reinnervation uses the residual nerves from an amputated limb and transfers them onto previously denervated alternative muscle groups. The muscles, newly reinnervated by a different group of nerves, then serve as biologic amplifiers of the amputated nerve motor commands.




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