Tech + Engineering

05
Mar

When State-of-the-Art is Second Best

At Chris Kort’s midtown Manhattan office, Eric has stopped by to try on his new foot. Kort, prosthetist and president of Prosthetics in Motion, has created a new, lighter device for him to try. It doesn’t look fancy—a carbon fiber socket and a thin springy foot plate made from carbon graphite encased in a specialized polyurethane liner. But Erik had a specific request—he wanted his foot to sit nicely in men’s dress shoes without breaking the back or bulging the front so noticeably. Erik slips his new foot into the black leather shoes he brought with him. Too much pressure here, too much tilt there, and Kort takes the foot back into the workshop, where his technicians alter the angle and bring it back out to try again. In the upstairs workshop, workers mold plaster, heat and stretch fiberglass, and sand down rubber hands and feet. This is a prosthetist’s office, and in many ways it more closely resembles an artist’s workshop than a laboratory.

Every few months, there’s exciting news about the latest in prosthetic technology. Most recently, the Department of Defense unveiled a hand with sensors that can feel pressure. Footage of the device is impressive—a patient uses his mind to control a robotic hand that can sense pressure, shake hands, and grasp delicate objects.

Chad Jukes high on Lobuche at about 19,000 feet. Photo by Didrik Johnck.
Sometimes, a less technological prosthesis works better. Here, mountaineer Chad Jukes climbs Lobuche in Nepal with a durable prosthetic leg.

Prosthetic technology is certainly advancing rapidly, but there’s a catch. For most people, these state-of-the-art devices are neither attainable, nor well suited for day-to-day life. In fact, for the average person, something far simpler is often in order. Yet what amputees need and what they get can often be quite different—and the question of what makes something “state-of-the-art” can be a confusing one.

One in every 190 Americans currently lives with a lost limb. But the person you generally see in televised breakthroughs is actually the exception when it comes to amputees. Only about 15% of amputees are trauma victims and cancer survivors—the types of patients who most often make good candidates for high-tech prostheses. About 80% of amputations are due to vascular diseases like diabetes. Weight gain, cardiovascular issues and general immobility make it hard for amputees with vascular diseases to get up and walking again at all after an amputation, let alone running around on a myoelectric leg.

Even those who are fit, mobile, and looking to get the most advanced technology then face the question of cost. A myoelectric arm, a design that uses a person’s own muscle contractions in the residual limb to control the device, can cost up to $100,000. The C-Leg, an above-the-knee prosthesis with a microprocessor in the knee, allows users mobility and flexibility, but can cost $70,000. Add a state-of-the-art foot to that and you’re looking at another $5,000.

“We waste a lot of money in getting people into technology before they understand what that technology’s value really is,” says Robert Radocy, an amputee turned prosthetist who founded TRS Inc.

Body Powered

It’s easy to watch video clips of dexterous and dynamic prostheses and think, who wouldn’t want that? But there are plenty of circumstances in which prescribing such a device would be a misunderstanding of what a patient really needs. In one study that explored the needs of amputee farmers, the researchers interviewed a man who was given a myoelectric arm—something that is not only expensive, but also completely unsuited for farm work. Myoelectric devices cannot get wet or dirty, two things that are nearly guaranteed during a day of farming. The farmer in question simply kept the arm in his closet—a $100,000 device sitting there gathering dust.

It’s not just farmers for whom specialty electric devices aren’t quite right either. When it comes to everyday users, myoelectric arms or microprocessor knees, for all their amazing technology, are sometimes not the best option. Radocy, an upper limb amputee, is an advocate for what are called body-powered prostheses. Rather than being controlled by a computer or sensors, a body-powered arm is far more like a series of bicycle brakes—the arm is strapped to the users body, and connected to a series of cables. By twisting his body one way or another, Radocy can open and close his hand. The system may seem low-tech, but Radocy argues that when it comes to performance, his body-powered hand can outperform even the most advanced myoelectric hands.

writing-with-prosthetic-hand
Body-powered prostheses can give users a surprising amount of dexterity and control.

“I’ve thrown the gauntlet down,” he says. “Show me someone who can do something thing better than I can, wearing a myoelectric arm. I’ve tossed down the gauntlet lots of times. The industry isn’t willing to pick it up.” According to Radocy, his body-powered upper-limb prostheses can grasp quicker and with more force than its myoelectric cousins. “I can grasp something in the air,” he says. “You can’t do that with an electronic hand.” And not only can he close and open his hand about as fast as a non-amputee could, he can also feel what he’s picking up. Because the amount of gripping force is coming directly from his body, Radocy can close his eyes and still move whatever he is holding.

With a myoelectric hand, that feedback isn’t there—in fact, the most recent advance in hand technology that many celebrated just this month was a hand that could provide some feedback to the user. Radocy already has that, and it’s far cheaper and more reliable than the electronic version. “The high performance prosthesis I wear is a fifth as expensive as the most expensive arm prosthesis. So I can buy five prostheses for the same price as an electronic arm.”

Skewed Incentives

That doesn’t always happen, though, even among patients for whom a low-tech solution may be best. While most prosthetists put their patients first, the way the industry is set up incentivizes reaching for that top-shelf prosthesis first. “One of the odd things about prosthetics is that we don’t get paid for our time. We are paid for the device,” explains Steven Hoover, who once worked as a prosthetist and now works on the manufacturing side for College Park, a company that makes prosthetic devices. The more expensive the device, the bigger the prosthetist’s paycheck. The result isn’t surprising—why fit someone with a $30,000 device when you can have them in a $100,000 one that seems fancier and sends you home with a fatter wallet? While Hoover says that the vast majority of prosthetists are honest, “at the end of the day there are still a few people in this field for the wrong reasons.”

That’s in part because in the United States, becoming a prosthetist is more like becoming a carpenter or engineer than it is like becoming a doctor. “Traditionally, way back in the early days of prosthetics, we were looked at as wood carvers, because we carved people’s legs out of wood,” Hoover says.

british artificial limb factory 1941
Representatives of the Allied governments visit the artificial limbs factory at Queen Mary's Hospital, Roehampton in 1941.

Today, there are two certifying boards in the U.S. for prosthetists: the American Board for Certification in Orthotics, Prosthetics and Pedorthics (ABC) and the Board of Certification/Accreditation (BOC). Both require prosthetists to have a bachelors degree, go through a specialized post-graduate course on orthotics and prosthetics, and complete a year long residency with a prosthetist before taking their board exams. This is compared to the six to eight years that most doctors spend in training.

Sometimes, the lower barrier to entry can draw people whose hearts aren’t exactly in the right place. “It’s hard to find a really great prosthetist in general,” says Jen Lacey, an amputee and patient advocate. “There are a lot of not so great prosthetists out there who don’t really listen to the patient. People normally go through a few different prosthetists before they find the one that’s the one.”

The Right Device

There has never been a scientific study comparing body-powered prostheses with electronic ones. But there may not need to be. Radocy, though a staunch advocate for body-powered devices, doesn’t believe there’s a single solution. He understands that not everyone might want a body-powered prosthesis that looks more like a clamp than a hand. And there isn’t the equivalent of a body-powered prosthetic arm for lower extremity amputations—prosthetic legs with articulated movement have to be electrically powered. What he does argue is that amputees should know what their options are before being wooed by a “state-of-the-art” device—especially in instances where a myoelectric arm may not hold up. “People should be given some choices,” he says.

2013 IPC Athletics World Championships
Dutch sprinter Marlou van Rhijn, running on carbon fiber blades, rounds the bend of the 200 m in the 2013 IPC Athletics World Championships.

In some cases, not wearing a device at all, or using a wheel chair instead, is the right choice. Many farmers with upper limb amputations decide not to wear prosthetic devices, even body-powered ones—they find them too hard to manage and even dangerous on the job. Christin Elnistky, a nurse and researcher at the University of North Carolina, organized a panel for women amputees to express their needs. One explained that while she was pregnant, it was using a wheel chair rather than her prosthetic leg that gave her the most ability to move around and stay independent. “Sometimes not wearing, or using another technology like a wheelchair, maximizes their independence,” Elnitsky’s research concludes.

No one is saying work on prosthetic devices should cease. The faster, lighter, cheaper, and more effective that science can make prostheses, the better it will be for everyone. “We have to develop things at both end of the spectrum,” Hoover says, “because that’s the only way we’re going to move things forward.” Without researchers pushing the boundaries of prosthetics, users will be stuck with the same systems forever. Prosthetic technology has advanced, but it’s nowhere close to mimicking human function yet. While research continues, amputees are faced with choices about how to maximize their mobility in a way that fits their needs and lifestyle.

surfer-with-prosthesis
This surfer competes at the 2011 Big, Bad, and Ugly Surf Contest, in Morro Bay, California, using a durable prosthetic leg. Conditions like these would damage today's myoelectric legs.

This, perhaps, is the most important aspect of the field—not the gadgetry or the motors or the electrodes or the sensors—but understanding each patient and what makes them the most independent. Elnitksy says that patients aren’t just equal partners in the conversation—they’re more like customers, there to receive a service. “I come to you with a service need, I can tell you what it is I want, you find a way to meet my preferences,” she says. The mark of a great prosthetist is one who can listen to those needs and preferences, figure out which device will work best, and fit that device properly to the person. Sometimes that device is an electric arm or a microprocessor knee. But sometimes it’s not.

Back at Kort’s office, the prosthetist is in the middle of a full day of fitting patients from across the mobility spectrum—from Erik, whom we met earlier, to Robert, a 79-year-old who lost his lower leg to osteomyelitis, a bone infection, and Ariel, a professor who was crushed by a New York City taxi and had to have both his legs amputated below the knee. For each, Kort figures out what they want to be able to do and tries to make it happen. Eric is still here for his dress shoe fitting. Ariel, who at the time of his accident was training for a marathon, wants to be able to run again. The measure of success for a patient isn’t how state-of-the-art their legs or arms are, but how well they can live their lives.

“I’ll know I’m fully recovered when I run that marathon,” Ariel says. Whether it’s on a set of carbon-fiber blades or a pair of hydraulically-damped metal legs doesn’t seem to matter to him.