Phantom limb pain is a common problem for people who undergo amputation, and so is the ability to function even with a regular prosthetic, but a medical advance that sounds like it comes straight out of "Star Wars" is giving at least one woman significant relief from that pain.
She now has a functioning bionic prosthetic hand that can feel some sensations and help her do about 80% of what she used to do with both hands.
While Luke Skywalker's human-like bionic hand is still years away, scientists say they are a step closer with this newest prosthetic technique, and doctors hope others will soon benefit from this approach.
Karin, whose full name is not disclosed in the proof of concept study published Wednesday in the medical journal Science Robot, had been using a regular prosthetic hand for years, but it was hard to control.
And as with even the most technologically advanced prosthetics on the market, it was uncomfortable and sometimes even painful to use.
On top of that, the Swedish 50-year-old, who lost her hand in a farming accident, had been living with excruciating phantom limb pain for more than 20 years.
"It felt like I constantly had my hand in a meat grinder, which created a high level of stress and I had to take high doses of various painkillers," Karin said in a news release from the group that made her new prosthesis possible.
The engineers and doctors who did this work are a part of the Center for Bionics and Pain Research, a multidisciplinary collaboration between several international organizations.
To relieve her pain and to gain function, she agreed to be a part of an experiment that would give her a bionic hand.
The team says she is the first person in the world with a below-elbow amputation to successfully get a bionic hand directly connected to her neuromusculoskeletal system.
Karin's prosthesis is considered bionic because it is attached to her nervous system as well as to the muscle and bone, unlike a traditional prosthesis that attaches to the end of her stump through suction or a harness and cable system.
Although some other kinds of implants require external equipment, the bionic hand is completely self-contained.
Surgeons embedded a controller, a wrist-shaped battery unit and a mechatronic coupler - a device used to transmit power - that connects to the neuromusculoskeletal interface, so she doesn't need any additional equipment like a large battery or processing unit.
However, there wasn't a lot of space in the area for everything to fit, so surgeons had to rearrange her muscle and nerves in what was left of her arm.
They also eliminated the neuromas, the disorganized group of fibers that ball up at the end of a nerve when it is cut.
Dr. Max Ortiz Catalan, a co-author of the new study and head of neural prosthetics research at the Bionics Institute in Melbourne, Australia, said the neuromas are what can cause some of the phantom pain when people lose a limb.
To get the signals from the brain to the bionic hand to tell it what to do and to give it a sense of touch, doctors transferred a muscle graft from the woman's leg to her arm so the nerves could reconnect to a natural target. Using the muscle also prevents the formation of new neuromas, Ortiz Catalan said.
Doctors then plant an electrode in that muscle, which works as a biological amplifier, boosting the electric signal from the brain into the hand, where AI algorithms inside the prosthesis interpret the signal and allow her to move the bionic hand.
Because the nerves are engaged in this process, Karin also has a limited sense of touch through the bionic hand.
Now she's able to hold and release objects with a wide variety of shapes, turn a door handle, pick up coins, prepare food, pack a suitcase and many more practical activities she couldn't do well before.
It's worked for three years, a good sign that it has been well-integrated into her body, researchers say.
Since the nerves are involved in an activity, Ortiz Catalan said, it also significantly reduces phantom pain. Her phantom pain level dropped from a five to a three, the study said, and her stump pain vanished entirely.
She said she's also been able to sleep better.
"We're expecting the pain to disappear," Ortiz Catalan said.
The hand has a fully customizable look. In Karin's case, it intentionally looks like a robot's so it can "be shown and not hidden," said Dr. Francesco Clemente, managing director of Prensilia, the company that developed the hand.
"We wanted the users to be proud of what they are, rather than ashamed of what was lost," Clemente said in a news release.
Catalan said this procedure in part developed out of his graduate school thesis, and he was thrilled to see that it can work.
"It's been a long journey," Catalan said.
Now he hopes to refine the technology and make it more accessible.
He's currently in Ukraine, where, he said, there are many more people who could benefit from a bionic hand.
"We're still far away from Luke Skywalker's hand," he said. "We're still not close to all the functions of a biological hand, but we definitely made a considerable step forward."
Dr. Jorge Gonzalez-Martinez, the Stuart Niles Rowe Chair in neurological surgery and the vice chair of the Department of Neurological Surgery at the University of Pittsburgh, said this is a "very important and impactful achievement from the group."
Gonzalez-Martinez, who did not work on this research but who has a team developing their own bionic hand and other robotic projects to help patients, said it's an exciting time for rapid advances in bionic technology.
Several groups in the U.S. and abroad are looking for ways to create these bridges between the nervous system, the body and the brain that interface with machines that can restore function to parts of the body that no longer work or are missing.
"I think what the article shows is pretty much in the scope, is absolutely great to have this implantable device in the hand that can control it and can perform what we call the pinching movement, one of the most important functions of the human hand," Gonzalez-Martinez said.
Such movement improves quality of life, but he said it is still "very rudimentary."
"This is a very, very simple movement that allows us to grab stuff, but it does not give us sensory feedback," Gonzalez-Martinez said.
In other words, a human hand has the ability to know exactly how much pressure it needs to pick up a hot cup of coffee versus something heavier like a laptop that requires more pressure. Gonzalez-Martinez's group and others teams are working to give a bionic hand more sensory ability.
The next hurdle is also the expense.
Governments have invested in this bionic technology, but more private sector help will be needed to make this technology widely accessible, Gonzalez-Martinez said.
For the patient in this study, though, her bionic hand - even with its limitations - has changed everything.
"For me, this research has meant a lot," Karin said in the news release. "It has given me a better life."
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