Fourteen years after amputation, research offers woman a new arm — a high-tech, thought-controlled prosthetic capable of nearly matching the dexterity of flesh and bone. By Scott Dance
Over the 14 years since losing her right arm to a hollow-point bullet, Dana Burke was convinced she could feel herself pointing, pinching or waving as she motioned with the 5-inch-long limb the attack left behind.
Still, she had to relearn how to pull her hair back in a ponytail and tie her shoes. It’s a struggle to play horsie with her three children using only one arm for support, and she had to start off with a child’s fat crayon to learn to write left-handed.
But now, she has proof of what she knew all along. A team of researchers watched in awe in her Central Pennsylvania home as she controlled a virtual arm depicted on a laptop through 11 distinct hand, wrist and elbow movements using just her brain and a set of sensors on her arm.
Burke soon will be one of the world’s first amputees to replace her lost limb with a high-tech, thought-controlled prosthetic capable of nearly matching the dexterity of flesh and bone.
It’s the fruit of a project at Johns Hopkins Applied Physics Laboratory six years in the making, intended to aid wounded war veterans. But Burke’s case is a medical marvel, her doctor said, that could change amputation surgery and recovery for all patients. “It shouldn’t really be possible with a typical above-elbow amputation,” said Army Capt Michael A Powell, a Hopkins graduate student researcher who developed the software that translates nerve impulses at the end of arms like Burke’s into virtual motion on a laptop screen — a small step away from controlling a robotic prosthetic.
For most patients today, prosthetic options use a tension cord or simple mechanics to control basic movements — at most, opening and closing a pincers and extending an elbow.
“Wow,” whispered Burke’s brother, Chris Griffith, as he watched his sister demonstrate not only pointing, pinching and waving, but flexing, rotating and extending in all directions.
While Burke isn’t surprised to have maintained the capacity she took for granted for the first 26 years of her life, the prospect of returning to normal made her giddy.
“I feel like a kid on a bike,” said Burke, looking the part as she bounced in her chair at her dining room table, flexing brainpower that had been lying dormant since she lost her arm. “I feel special.”
Dr Albert Chi, a trauma surgeon at Johns Hopkins Hospital, said Burke is indeed special.
Chi has been working for the past year with researchers at the Johns Hopkins Applied Physics Lab and patients who could benefit from the prosthetic technology.
To make it work, Chi figured patients would require surgery to replant nerve endings detached during amputation into muscle at the arm’s end. That would restore muscle stimulation at the amputation site, enabling detection of intended movements for the missing limb.
Burke stumbled across Chi by way of a blurb in Popular Mechanics her father saw that highlighted the physics lab’s work developing the most lifelike prosthetic arm ever assembled. The device, only six of which exist, is considered the most advanced ever created, with nearly all the dexterity and precision of a real arm. After an Internet search and a phone call, she was on the line with Michael McLoughlin, manager for the modular prosthetic limb project at the applied physics lab.
McLoughlin referred Burke to Chi, who met with her to prepare for the surgery, known as targeted muscle reinnervation. But it turned out she didn’t need the surgery. When she later visited the lab this spring and was connected to the arm, she almost immediately was able to control it. “It was amazing,” Chi said. “My jaw almost hit the floor.”
Chi found that after Burke’s amputation, the surgeon reattached loose nerves to the muscle that remained above where her elbow once was. That meant that when her brain sent signals down toward the hand, instead of disappearing into her tissue, they were transferred to muscle in the rounded end of her arm. “It was a progressive thinker, whoever did that surgery,” Chi said. “It was against the norm.”
The researchers are in the midst of 10 straight days of visiting Burke at her home and fine-tuning her control of the virtual device. They plan to outfit her with the real thing — a slightly simpler version of the lab’s modular prosthetic limb — by February 1.
The scientists’ efforts began in 2006, under a programme of the US military’s Defense Advanced Research Projects Agency known as Revolutionizing Prosthetics. The government hired the Hopkins applied physics lab in 2010 for the $35mn job of managing development of the arm, as more and more soldiers returned from Iraq and Afghanistan with amputations.
“What’s available commercially is woefully inadequate,” Col Geoffrey SF Ling, a physician and war veteran who manages the military programme, said that year. “We also set the bar really high. We want to give them back their lives.”
Since then, McLoughlin and researchers have tallied up 3,000 hours of experience with the device, fine-tuning the technology that directs its movement. Sensors placed around an amputated arm detect patterns in firing muscles when subjects are told to imagine making particular movements. Once a pattern is established, it can be assigned to an action; the more complex the pattern data collected, the more lifelike the movement.
“It’s almost more important than colouring it right,” said Bobby Armiger, one of the physics lab researchers, of amputees’ need for prosthetics that mimic human motion as much as possible.
Such thought-controlled robotic motion has been achieved in the past. Under an earlier project sponsored by the military research agency, Duke University researchers taught monkeys to operate a robotic arm by thought alone, but that was through wires implanted in their brains. In another venture, a patient at the Rehabilitation Institute of Chicago was able to operate an arm using sensors attached to his chest muscles, to which arm nerves had been grafted.
But the modular prosthetic limb project goes beyond both, the Hopkins researchers said, because it doesn’t require any sensors to be implanted, and, as in Burke’s case, doesn’t even require surgery. — The Baltimore Sun/MCT