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Roseann Sdoia, a Boston Marathon bombing survivor, tries out a new leg at Next Step Bionics, Inc. in Newton, Mass.
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When the National Academy of Sciences established the Artificial limb Program in 1945, the options for amputees were few: crude, wooden prostheses. And for those who chose none: life confined to a wheelchair. Fast-forward 65 years and the United States faces an influx of amputees from the conflict in Iraq, but the opportunities for soldiers returning home from war with an amputation are far more advanced. Listed are some of the most important advancements in robotic prosthetics in the last 20 years that give artificial limbs more function than ever before.
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1. Prosthetic Foot Materials
For years, wood was the dominant material for a prosthesis. But over the last 20 years, materials have emerged to give greater comfort and confidence for amputees. Susan Kapp, an associate professor of orthotics and prosthetics at the University of Texas Southwestern School of Health Professions, says if a prosthetic foot is cut open, most likely the material found inside is carbon fiber. Carbon fiber, according to Kapp, is a much more life-like material, giving amputees a sense of life in their foot. Thermoplastic sockets give prosthesis recipients extended comfort at the site the prosthesis is fitted, and titanium gives a prosthesis longer life and durability.
U.S. Army/ Roger J. Mommaerts Jr.
Bluetooth technology made the jump from the cell phone industry to prosthetics in 2007 when Marine Lance Cpl. Joshua Bleill received two artificial legs after seeing combat in Iraq. Each leg was fitted with a Bluetooth device. Bluetooth is more often recognized for its ability to connect pieces of technology together without the use of wires. In Bleill’s case, the Bluetooth devices communicate with each other to regulate stride, pressure and speed in the prosthetic legs. The benefit of Bluetooth technology, according to Ryan Blanck, a prosthetist at the Center for Prosthetics and Orthotics at Brooke Army Medical Center in Ft. Sam Houston, Texas, is the programmability of the software. “We can take that technology an further develop it to adjust to a patients need,” Blanck said.
3. Microprocessor Knees
With an onboard computer within the prosthesis, people with above-knee amputations have greater control over walking, stopping and moving on inclines. These “robotic” knees, termed microprocessor knees, analyze the pressure an amputee puts on the missing limb. Also contained within the knee is a fluid control unit, which the microprocessor monitors to appropriate joint resistance when walking on inclines. Available since the early 1990s, microprocessor knees have revolutionized the arenas of safety and stability for people without knees. Kapp says people that receive the prosthesis don’t have to worry about the knee buckling under them.
Touch Bionics Inc. and Touch EMAS Ltd.
4. Myoelectric Technology
When the i-LIMB hand debuted in the United Kingdom in July 2007, people caught a glimpse of the future of robotic prosthetics. The i-LIMB applies myoelectric technology, where the prefix myo- denotes a relationship to muscle. Myoelectric prostheses are controlled by placing muscle sensors against the skin at the site of amputation. The electric signals generated by the muscle at an amputee’s stump controls a processor aboard the prosthetic. This myoelectric technology allows for greater control and precision in the five fully functional digits, enabling recipients to perform everyday tasks such as picking up coins and opening tabbed aluminum cans.
5. Targeted Muscle Reinnervation
Amputees are in the infant stages of controlling prostheses directly with their minds. Through targeted muscle reinnervation, the nerves from the amputated limb are reenergized in a different part of the body, for example, the chest. When an amputee wants to use their arm in a particular fashion, he or she thinks the action, prompting the nerves in the chest to react. That reaction sends a message to a microprocessor in the robotic limb, which performs the action. Currently, there are only 35 people in the world with TMR limbs, and Blanck has fit 14 of them. He says the ever-changing prosthetic field aims to allow an amputee think about their prosthesis in a way that is normal. Jesse Sullivan (left) was the first man to receive this treatment technique from the Rehabilitation Institute of Chicago, and Claudia Mitchel (right) was the first woman to receive it.
When bombs rocked the Boston Marathon last year, emotional reverberations were felt throughout the country: Communities held memorial races and sported Boston Strong ribbons and shirts, created makeshift memorials out of running shoes and American flags, donated money to families of injured runners. Engineers, meanwhile, got down to the nitty-gritty: Building better prosthetics for the 16 survivors who lost limbs that day.
"I think Boston raised awareness and is kind of inspiring for promoting recovery instead of focusing on the injuries," said Levi Hargrove, Director of the Neural Engineering for Prosthetics and Orthotics Laboratory at the Rehabilitation Institute of Chicago. Even though his lab hasn't worked directly with survivors, everyone in the field has felt the impact, he said.
"The survivors are getting back to their lives, working with scientists and therapists, because they're going to be living with this condition for a long time," Hargrove said.
Last month, one of those survivors took the stage at TED2014 and showed off her first-of-its-kind bionic leg that allows the professional ballroom dancer to rumba again. After Adrianne Haslet-Davis danced, she tearfully thanked Hugh Herr, director of the Biomechatronics Group at The MIT Media Lab and creator of the leg.
"All this emotion poured out," Herr said. "The very first time she [tried the new leg], she was ecstatic. She was so joyful about being on that dance floor and feeling that freedom again."
Herr, whose lab partnered on a fund to support the development of specialized prostheses for runners after the Boston attack, based Haslet-Davis's leg on data he gathered from dancers of a similar build and body type to Haslet-Davis's. He invited the dancers to his lab, which was tricked out with sensors to track exactly how they moved and how their forces impacted the dance floor.
The idea, he said, was to extract those principles of dance and imbed them into chips on the bionic limb.
"It's responsive in a way that's appropriate biomechanically," he said. "It doesn't simply output a traditional trajectory that she would have to keep up with like a wind-up toy. It's more like she is the lead and the limb is the partner."
The leg also has to be able to move like flesh and bone, so the lab uses a "smart" material that can flop and stiffen depending on the voltage being applied from the body.
David Sengeh, a graduate students who also works in Herr's lab, recently won the Lemelson-MIT National Collegiate Student Prize Competition for his work on improving the sockets used in prosthetics. Conventional molding methods often result in prostheses that don't fit precisely, and often cause pain. Sengeh uses MRI and a 3D printer to create a design interface based on individual data.
"The goal is to make a model where you can enter someone's data, press play and get a comfortable socket," said Sengeh, who tested the method on one of the Boston survivors.
The end result? Without the short skirt she wore at her TED performance to show off the leg, it may have been impossible to tell she wasn't born with that leg.
The BiOm Ankle System was the first bionic ankle-foot device commercially available for lower-extremity amputees.iWalk Inc.
"My first dance happening to be so near the anniversary of the marathon bombing stands as a reminder that I'm a survivor, not a victim," Haslet-Davis said in a statement.
Because the bombing occurred at a time when the field of prosthetics was on the verge of new developments, success stories like Haslet-Davis's were able to quickly come to fruition. Previous research and development was primarily funded through the military's Defense Advanced Research Projects Agency and focused on veterans who had lost limbs in combat, but"a lot more individuals have had amputations for a variety of reasons, including young people in motor vehicle accidents, people in farming accidents, etc.," Hargrove said.
"The Boston bombing kind of broadened the horizon," Hargrove said.
Since most of the survivors were runners or otherwise very active, most will need multiple prostheses designed for different activities. Herr, a double amputee himself, says his closet is filled with different types of prostheses the way most people's closets are filled with shoes. As for a device that would go from ballroom dancing to grocery shopping to rock climbing to running…"No one's working on it yet," Hargrove said.
Still, mind-controlled prosthetics should soon make daily living much easier. Hargrove's team built a prototype of an above-the-knee prosthetic for daily living that should be "ready to send home with someone" in a couple of years.
"We're trying to allow people to perform functions like walking and then seamlessly going up and down stairs, that help you get around for daily living," he said.
This year, survivors may watch the marathon from the sidelines. But Herr predicts that at least one or two of the survivors will return to Boston one day to run the marathon again; the technology already exists to enable runners to do distances even beyond the marathon.