Building a Better Arm: An Amputee Helps Engineer His Own Future

This is part of a series of stories on design and disability from the July-August 2009 Utne Reader. For more read “Form and Fashion,” “Prosthetic Power,” “The Future of Prosthetics,” and “The Hype and Hope of Prosthetics.”

Ever since the first few amputees returned from Afghanistan in 2001, media coverage has often emphasized the medical care that saves their lives, and the advanced prosthetics they wear, with phrases like bionic arms and thought control.

The chasm between what people think is out there and what is actually available to an amputee has existed for years. The hype isn’t limited to the popular press: Scientific research and scientific literature repeat these claims. The first myoelectric prosthetic arm was demonstrated in 1955. That presentation included a powered hook that looks remarkably like one I got from Walter Reed Army Medical Center. In 1965 a New York Times headline proclaimed “New Process Will Help Amputee to Control Limb with Thought.” In 2007 a Popular Science article described a prototype robotic hand as “mind controlled” and “dexterous enough to play the piano.” The headlines have stayed the same, but, as I discovered, so has the technology. These prosthetic “concept cars” have historically had little effect on what most arm amputees actually wear.

Let me be clear: No expense has been spared on providing military arm amputees with the most cutting-edge technology available. Amputees at Walter Reed get the works–myoelectric and body-powered prosthetic arms with any attachments we might want, sports and other task-specific arms, cosmetic arms painted with the tattoos we used to have, you name it. In 2006 the Department of Veterans Affairs spent $1.6 billion on prosthetic devices and services. It’s the best insurance and the best care in the world, but that doesn’t change what there is to buy or what it can do.

The body-powered prosthetic split hook I chose instead of the myo arm has been characterized by some as little more than a rubber band and a stick. But the surprisingly useful mechanical design has endured for close to a century. Body-powered prosthetics have cable controls that you move by shrugging and tensing your shoulders, an action that opens and closes a simple hook or hand appendage. After trying everything else, I opted to wear this arm.

Mine is indistinguishable from those worn by amputees after World War II, except in materials: silicones and plastics in the socket, carbon fiber instead of wood or fiberglass in the frame, titanium instead of steel in the hook, synthetic fiber instead of steel cable for control.

Imagine this pace of development for other everyday products. We would make our calls on big black rotary-dial telephones (lightweight carbon fiber body!) and add figures using punch cards (improved design!). If this seems preposterous for other industries, why is it the reality of the prosthetic arm industry?

The problem is the size of the market, which is just too small to provide any real incentives for innovation. In the modern conflicts in Iraq and Afghanistan, 862 U.S. troops have become amputees; only 186 had lost arms as of February 2009. The total arm amputee population in the United States is estimated to be under 100,000. Anyone who approached a venture capitalist with a business plan with significant technical challenges and only tens of thousands of potential customers would be laughed out of the room. The government is, and will remain, the only game in town as far as research and development in prosthetic arms.

The same year I lost my arm, the Defense Advanced Research Projects Agency (DARPA) began the Revolutionizing Prosthetics program, whose costs now total nearly $100 million. The program was split into two parts: The 2007 project, headed by DEKA Research and Development Corp., was given a two-year deadline to make a prosthetic arm with the world’s best existing technologies.

The 2009 program is spearheaded by Johns Hopkins University’s Applied Physics Laboratory. APL’s goal is to create prosthetics that would, as the hype had it, be “thought controlled.” But the team wanted more than control for amputees; they also wanted to restore the ability to feel heat, cold, pressure, and surface texture. I found out about the program at Walter Reed when I was first being fitted for prosthetics, and I was anxious to get on board. Now I’m one of more than 300 engineers at over 30 institutions worldwide working on the APL project. I’m helping with suspension (attaching the arm to the body), grasping control, and system design.

At this point, no one is even trying to make a hand that will let a user win a Rubik’s Cube competition or play the piano. It’s just not yet possible to perform tasks that require such dexterity in real time.

Though both DARPA projects come close to living up to the hype that surrounds them, they must become real products in order to help anyone. We need to push the arm that last mile to the consumer.

As I discovered the difference between the science fiction and the reality of prosthetic arms, I tried to come up with a solution. So some friends and I started the Open Prosthetics Project as an online clearinghouse for sharing arm designs. The project attacks the most obvious barrier to innovation by giving people a forum in which to share their ideas. We want users and technicians to improve and tweak the technologies they use instead of being stuck with whatever one-size-fits-most device they get (for example, there is a section on our website called “Pimp My Arm”). A technically inclined amputee or technician can download our computer-aided-design files, modify them, and send them to a machinist.

The best way to really move prosthetics research forward is to hitch a ride on a real market. If we can find an application for a myoelectric human interface in the $32 billion worldwide video-game market, for example, we can tap into a massive reserve of people who might not otherwise get involved in the effort.

Another possible application is robotics. Prosthetic arms aren’t the only devices that require centrally controlled powered joints. The compact and powerful motors designed for the APL project could be useful in bomb disposal, hazardous waste inspection, and home-service robotics, for example.

The greatest revolution of all may be apparent only after the frenzy of prosthetics research spending has evaporated. The design evolution for which DARPA is laying the groundwork could come from any quarter, inside or outside the prosthetics industry. And who knows–someone might even make money doing it.

Excerpted from IEEE Spectrum (March 2009), “a monthly magazine for technology innovators, business leaders, and the intellectually curious”; © 2009 IEEE

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