Amputees often have the sensation that their missing appendages are still there, a phenomenon known as a phantom limb.
For Dennis Aabo Sørensen, the sensations he felt recently weren’t phantom. They were real.
The 36-year-old Danish man recently became the first amputee in the world to experience sensation in real-time thanks to an experimental prosthetic wired to his nerves.
“The sensory feedback was incredible,” he said. “I could feel things that I hadn’t been able to feel in over nine years.”
No Sensations for Nearly a Decade
Sørensen lost his left hand during an accident nine years ago. After a firework exploded in his hand, he was rushed to the hospital where his hand and forearm were amputated.
Since then, he’s been wearing a typical commercial prosthetic hand. It detects movement in his stump, which allows him open, close, and hold onto objects. However, he has to watch his every move to make sure that he doesn’t crush what he’s holding, whether it’s food or his child’s hand.
“It works like a brake on a motorbike,” Sorensen said. “When you squeeze the brake, the hand closes. When you relax, the hand opens.”
New Technology Makes the Phantom Limb Real
On Jan. 26, 2013, Sørensen underwent experimental surgery in Rome led by a specialized team of surgeons and neurologists. He was outfitted with a new type of prosthetic hand developed by a team of experts at the Swiss Federal Institute of Technology and the Scuola Superiore Sant'Anna in Italy.
Using four “transneural electrodes” implanted into what remained of his ulnar and median nerves, Sørensen was able to use an artificial hand outfitted with sensors that send touch information to his brain.
Researchers developed the hand by fine-tuning its electrical feedback. Normally, electrical currents are too coarse, and the human nervous system cannot understand them. But researchers used computer algorithms to find the right signals to turn these electrical snippets into an impulse the body could interpret.
Even while blindfolded, Sorensen could detect the shape and consistency of different objects, something never done before with a prosthetic limb.
“When I held an object, I could feel if it was soft or hard, round or square,” Sørensen said, adding that his children have nicknamed him “The Cable Guy” because of the wires coming from his hand.
Unfortunately, due to restrictions on clinical trials, Sørensen was unable to keep his new bionic hand.
A New Avenue for Amputees
Besides being the first time an amputee was able to feel in real-time, it was also the first time electrodes have been successfully implanted into an amputee’s peripheral nervous system.
“We were worried about reduced sensitivity in Dennis’ nerves since they hadn’t been used in over nine years,” said Stanisa Raspopovic, first author of the study, which was released today in the journal Science Translational Medicine.
Those fears quickly went away as Sørensen successfully operated the hand.
While it may sound like something from Star Wars or RoboCop, it’s not. However, researchers said that while this is a first step towards a bionic hand, it’s years away from being commercially available.
But giving one amputee an afternoon of experiencing touch again. Sørensen recalled that his doctor said he would more likely be grateful for what he had instead of feeling sorry for himself.
“He was right,” Sørensen said.