First mind-controlled bionic leg a 'groundbreaking' advanceFirst mind-controlled bionic leg a 'groundbreaking' advance
After losing his lower right leg in a motorcycle accident four-and-a-half years ago, 32-year-old Zac Vawter has been fitted with an artificial limb that uses neurosignals from his upper leg muscles to control the prosthetic knee and ankle. The motorized limb is the first thought-controlled bionic leg, scientists at the Rehabilitation Institute of Chicago reported Wednesday in The New England Journal of Medicine.
“This is a groundbreaking development,” says lead author Levi Hargrove, a biomedical engineer and research scientist at RIC. “It allows people to seamlessly transition between walking along level ground and going up and down stairs and slopes.”
Until now, only thought-controlled bionic arms have been available to amputees.
When Vawter thinks he wants to move his leg, the brain signal travels down his spinal chord and through peripheral nerves and is picked up by electrodes in the bionic leg. Unlike robotic models currently on the market, the prosthesis allows a normal, smooth gait no matter the incline. Although the cost hasn't been determined, a version could be available to the more than one million Americans with leg amputations within three to five years, the Chicago scientists said.
“It makes a phenomenal difference,” says Vawter, a software engineer from Yelm, Wash., whose right leg was amputated through the knee in 2009 after he crashed his motorcycle. Aware of the institute's work on bionic arms, Vawter and his surgeon contacted Hargrove and the team developing the pioneering prosthesis. For nearly three years ending in October, 2012, Vawter would travel to the institute periodically.
Vawter would remove his mechanical leg, slip into the bionic one, and run through a set of experiments the scientists devised, suggesting improvements and providing feedback on what was working and what was not.
Now, after multiple revisions to the leg’s software and two major revisions to the leg’s mechanics, Vawter says he can walk up and down stairs the way he did before the accident. With his mechanical leg, Vawter says, “My sound leg goes up every step first, and I’m just dragging the prosthetic leg along behind me.” But with the bionic leg, “I go leg over leg,” he says. “The bionic leg listens to the various signals from my nerves and responds in a much more natural way.”
Some current prosthetic legs are purely mechanical, like Vawter’s; others are robotic and have a motor, a computer, and mechanical sensors that detect how much weight is being put on the prosthesis and the position of the knee. These allow people to walk well but don’t allow people to seamlessly ascend or descend stairs with a normal gait or to reposition their leg while sitting without manually moving it. The thought-controlled bionic leg is much more sophisticated. In additional to mechanical sensors, it has two motors, complex software, and a set of electrodes - essentially antennae - in its socket that pick up the tiny electrical signals that muscles in the upper leg generate when they contract.
Two electrodes pick up signals from the hamstring muscle, where the nerves that had run through Vawter’s lower leg were redirected during the amputation. “So when Zac is thinking about moving his ankle, his hamstring contracts,” says Hargrove.
More electrodes pick up signals from other muscles in the residual limb. The complex pattern recognition software contained in the on-board computer interprets these electrical signals from the upper leg as well as mechanical signals from the bionic leg and “figures out what Zac is trying to do,” says Hargrove.
The U.S. Army’s Telemedicine and Advanced Technology Research Center funded the Chicago study with an $8 million grant to add neural information to the control systems of advanced robotic leg prostheses. Devising a thought-controlled bionic leg has been more challenging than a thought-controlled bionic arm, says Hargrove.
That's because the motors must be powerful enough to provide the energy to allow someone to stand and push along -- and they must be small. Also, the computer control system must be safe.
“If there is a mistake or error that could cause someone to fall, that could be potentially catastrophic, and we want to avoid that at all costs,” says Hargrove.
The leg is a prototype so Vawter cannot take it home. Error rates in the software are small but need to be made smaller, says Hargrove and the leg itself needs to be made quieter and lighter. In addition, prolonged use can produce chafing where the residual limb contacts the electrodes in the bionic leg’s socket.
The ultimate cost of the final product is unknown, says Hargrove, although upper extremity prostheses range from $20,000 to $120,000. "We are leveraging developments in related industries to make sure we use low-cost components whenever possible," Hargrove told NBC News.
Careful engineering will make it affordable. His goal is to restore “full ability” to all patients, especially the elderly. “This could mean the difference between living in their home longer and having to go to a nursing home,” says Hargrove.
New Bionic Hand Restores Sense of Touch
A new bionic hand has for the first time helped a man feel the objects he is holding and tell how big they are and whether they’re hard or soft.
It’s the first time anyone using a prosthetic has been able to really feel what he’s picking up, and it’s the latest development in field that has allowed people to control prosthetic devices with thought alone, and to manipulate objects with ever-increasing dexterity.
“It was quite amazing because suddenly I could feel something that I hadn’t been feeling for nine years,” said 36-year-old Dennis Aabo Sorensen of Aalborg in Denmark, who lost his hand and part of his arm in when a faulty fireworks rocket exploded as he lit it in on New Year’s Eve 2004.
It’s not quite ready for prime time. Sorensen had to undergo delicate surgery to have electrodes implanted in the nerves of his upper arm, and then months of training to use the device.
Silvestro Micera of the Ecole Polytechnique Federale de Lausanne in Switzerland and colleagues at the BioRobotics Institute at Scuola Superiore Sant’Anna in Pisa, Italy, developed the device, which is described in the journal Science Translational Medicine.
They had to equip the artificial hand with sensors to detect an object’s pliability and shape and translate this into an electrical signal. They had to figure out how to translate this signal into something a human nerve could understand and conduct to the brain.
Implanting the electrodes alone took seven or eight hours of surgery, Sorensen said.
But once it was all up and working, it worked well.
Sorensen was blindfolded and given a hard piece of wood, a stack of plastic glasses and a cotton pack, and he could tell them apart. He was also able to tell when he was handling a bottle, a baseball or an orange.
“My kids thought it was cool,” he said.
Sorensen’s since had to give the arm back for more refinement, and all the testing was done a year ago.
“They have to make it even better,” he said. Was he disappointed at having to go back to a more standard prosthetic? “Not really,” said Sorensen. “Now that I know it is possible, that is the key thing."
Paralyzed Mom Walks Again With Robotic Exoskeleton
When Marcela Turnage, 32, got out of her wheelchair and took her first steps with the aid of a robotic exoskeleton, she was so excited that she started screaming.
“It was so amazing. I was overwhelmed with joy,” says the 32-year-old mom from Baltimore. Following a 2002 car accident that killed her boyfriend, Turnage, then 19, was paralyzed from the waist down due to a spinal cord injury. Doctors told her she would never walk again.
Today, she is one of a growing number of patients who are regaining mobility with the FDA-approved ReWalk exoskeleton. The bionic suit helps people with spinal cord injuries walk by using accelerometers (akin to those in iPhones) to detect subtle changes in their balance.
The suit, worn outside of clothing, moves the users’ legs in a natural gait, while the person uses crutches for stability, explains Peter Gorman, MD, associate professor of neurology at the University of Maryland School of Medicine and chief of the division of rehabilitation at the University of Maryland Rehabilitation & Orthopaedic Institute (UMROI).
“I find this technology extremely exciting—and patients really love getting out of their wheelchairs and walking with this system,” says Dr. Gorman, who is planning a small study of the benefits of the ReWalk device, which costs about $80,000. The bionic suit is currently available at about two dozen rehab facilities in the United States, according to its manufacturer.
“An exhilarating sense of freedom”
Marcela Turnage, photo courtesy University of Maryland Rehabilitation & Orthopaedic InstituteTurnage says that using the exoskeleton twice a week in her rehab sessions at UMROI has brought her “happiness, hope, and an exhilarating sense of freedom.”
During her 11 years in a wheelchair, Turnage attended college, found a new love, got married, and had a daughter, now age 7. She also works full time and is able to drive, using a car with special hand controls.
When Turange started using the ReWalk device in September 2013, “I felt like a baby again, learning to take my first steps," she says. "My first reaction was to be a little bit afraid, not knowing what to expect.”
Using the robotic device was particularly challenging for Turnage because she wears a prosthesis on her left leg, which was amputated above the knee after the accident.
“I have always lived with a feeling of shame about not having my leg,” Turnage says. “But when I stood up and walked for the first time, the incredible joy erased that shame,”
The mom adds, “Learning to use ReWalk is a process and every time I wear it, I learn something new. I can feel myself getting stronger.”
The Exoskeleton’s Surprising Health Benefits
While helping paralyzed people walk again is the most obvious benefit, says Dr. Gorman, “the ReWalk exoskeleton also appears to improve their health by improving digestion and bowel function, which can be adversely affected by years of sitting in a wheelchair.”
The manufacturer reports that the bionic suit, designed for spinal cord injury patients who retain use of their arms, may also help reduce several other disorders linked to long-term wheelchair use, including bone thinning, pressure sores, and problems with breathing, blood circulation, and urination.
There are currently two models: the ReWalk Rehab 2.0, which is FDA-approved for use in clinical settings, such as rehab centers, and a personal version for home use, which is currently available in Europe and is awaiting FDA clearance for use in the US.
Helping Paralyzed People Stand Tall—and Walk Freely
Turnage reports that the exoskeleton has had another amazing effect. “I have pretty strong pain from sitting in a wheelchair for so many years, but using the robot has minimalized my pain level. I can feel all the pain in my body going away.”
Along with combatting her chronic pain, the device has literally helped the mom stand tall. “It’s so wonderful to be able to see people eye-to-eye with no help from anyone. The more I’ve trained in walking with the robot, the more I feel independent.”
In addition, she says, “Using this device is all about hope, that people with spinal cord injuries shouldn’t give up. Today, it’s the ReWalk and tomorrow, something even better will come along—maybe even the cure.”