‘I control robot limb by my thoughts’
The arm has changed the life of the 24-year-old motorcycle accident victim, allowing her to cook, put on make up, clean the house and carry shopping bags with relative ease.
She found a previous prosthetic limb that relied on conventional technology virtually useless and ended up wearing it chiefly for cosmetic reasons.
The woman told doctors: “I just think about moving my hand and elbow, and they move.
“My original prosthesis wasn’t worth wearing — this one is.”
Most electronic artificial limbs allow only a single motion to be controlled at a time.
Elbow, wrist and hand movements have to be carried out sequentially and are slow and awkward.
Conventional prosthetics also have no sense of touch and provide little sensory feedback to the user.
The new limb, developed by engineers and surgeons in the US, uses amplified signals from the patient’s own nerves to trigger a much wider range of movements. It also allows a degree of feeling.
Severed nerves are re-routed to muscles in the upper chest, which act as “bio-amplifiers”. They direct the signals once sent to the amputated arm to surface electrodes, which relay them to the robot limb.
Doctors also re-routed sensation nerves to the hand to a patch of skin on the patient’s chest. Now when this patch of skin is touched, she “feels” the sensation of something touching her missing hand.
The team, led by Dr Todd Kuiken, from the Rehabilitation Institute of Chicago, wrote: “With training, the patient became proficient in use of the prosthetic within a few days.
“She was able to operate the hand, wrist and elbow simultaneously. She reported that operation of the hand and elbow was very intuitive: when she thought of opening the hand, closing the hand, bending the elbow, or straightening the elbow, the prosthesis responded accordingly.”
Pressing pressure-sensitive buttons allowed the wrist to rotate at the same time as other movements were being made. The patient learned to use the limb for an average of four to five hours a day, five to six days a week, for a wide range of everyday activities.
She had previously used the conventional prosthesis only once or twice a month, mainly to improve her appearance.
Three other patients had also been fitted with artificial limbs using the new “targeted muscle reinnervation” technology.
The scientists wrote: “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.
“Long-term follow-up is also needed.”
