Glen Lehman, a retired sergeant first class in the United States Army who received Targeted Muscle Reinnervation (TMR) surgery after he lost his arm in Iraq, stands with his bionic arm next to LTC Martin Baechler, M.D., a surgeon at Walter Reed Army Medical Centre, during a presentation of the latest in TMR, a bionic limb technology.
Credit: AFP
WASHINGTON: A bionic prosthetic arm that is controlled by its operator's thoughts and feels like the amputee's lost limb went on display at a major U.S. science conference.
More than 50 amputees worldwide, many of them military veterans whose limbs were lost in combat, have received such devices since they were first developed by U.S. doctor Todd Kuiken in 2002.
The arm uses technology called Targeted Muscle Reinervation (TMR), which works by rerouting brain signals from nerves that were severed in the injury to muscles that are working and intact. "What we do is use the nerves that are still left," Kuiken said. "Muscle becomes the biological amplifier."
Trained and intuitive arm
Glen Lehman, a retired U.S. military sergeant who lost his arm in Iraq, demonstrated the latest technology at the annual conference of the American Association for the Advancement of Science in Washington.
"It feels great, if feels intuitive. It is a lot better than the other prosthetic I have now," said Lehman, whose forearm and elbow were blown off in a Baghdad grenade attack in 2008.
"The other one is still controlled by muscle impulse, you just flex muscle to make it move, it is not intuitive. This arm is more trained to me, whereas the other arm I had to train to it," he said. "It does feel like my own hand."
How hard to squeeze?
Lehman demonstrated for reporters how he could pinch his finger and thumb together, lift his forearm and bend his elbow, and turn his wrist just by thinking about those actions.
Kuiken said more advances, such as the ability to transfer some sensation to the limb, are being studied in the lab but have not yet made it to patients.
Other drawbacks include the inability to sense how hard the battery-powered prosthetic hand is squeezing, but Kuiken said scientists are working on ways to improve the technology with added sensors.
"Our goal would be to put sensors in the prosthesis to, for example, know how hard you are squeezing and then bring that up and have a device squeeze on this area (of the bicep) so the patient has an idea of how hard he is squeezing."
Kuiken said the team has encountered some technological "challenges" that have slowed progress but is "excited about moving forward".
