Imagining a bionic future

Reading nerves
Researchers have enabled communication between the prosthetic device and the wearer through a technology known as Targeted Muscle Reinnervation, or TMR, which involves taking remaining nerves from the amputated limb and placing them, in this case, in the pectoral area of the chest where electrode sensors read signals for movement. Proto 2 also incorporated injectable myoelectric sensors which serve a similar function as electrodes but can be implanted or injected into the body.

“We look at these signals with pattern recognition software and then we’re able to allow the limb system to interpret these patterns,” said Harshbarger. “The limb learns what the patterns are and the person has to think only about the movement.” The team hopes a future model, which will incorporate sensory feedback, will be tested by the Food and Drug Administration and be publicly available by 2009.

Harshbarger believes the technological advancements of the project will benefit not only amputees, but also people affected with mobility-limiting diseases like Parkinson’s or spinal cord injuries.

“An [amputee] who is healthy and given the right tools can live a healthy and productive life,” he said. “Without those tools, it really changes your outcome.”

Since upper extremity limb loss accounts for a majority of all amputations each year, and thus draws fewer research dollars, the government hopes its investment will improve technology for arm and hand prostheses.

In addition to the Proto 1 and 2, an array of groundbreaking prosthetic devices have been developed by private companies and academic researchers in the past year, including a myoelectric prosthetic device with motors in each finger joint, a motor-powered ankle-foot, and an artificially intelligent knee. Creators of the devices have puzzled over how to provide power to a prosthetic limb without adding weight, how to most efficiently enable neural or nerve communication between the device and the wearer, and how to provide the functionality and appearance of a native arm.

More projects are underway; in late September, the Department of Defense awarded Idaho State University with an $842,000 grant to build a “smart” prosthetic hand capable of grasping, lifting and twisting as well as responding to sensory and visual feedback.

Yoky Matsuoka, a recently appointed MacArthur Fellow and an associate professor of Computer Science and Engineering at the University of Washington, is aiming beyond DARPA’s four-year deadline with visions of an anatomically correct and life-like robotic hand that could be transplanted on an amputee. Made of composites and metals with a polymer exterior, the hand would connect directly to the nervous system and allow an amputee to use it instinctively.

Paul Selmer, the small airplane enthusiast, is eager to see what new technologies are developed next, but said the most revolutionary innovation in his life switching from a wool sock liner to a custom-made silicone gel liner. For years, Selmer followed his fitter’s instructions and placed wool socks between his prosthesis and his stump to provide cushioning, but often developed painful sores. The new liner not only cushions the bone protrusion but it also draws sweat away from his body, helping to prevent chafing.

“I used to spend two or three days waiting for sores to heal up, but with this technology, I can just keep going,” he said.

Jeff Brandt, CEO of Ability Prosthetics & Orthotics and Selmer’s prosthetist, pointed to another low-key revolution in the field: customization. Brandt, who studied with the prosthetics researcher responsible for developing TMR technology, expects a permanent shift towards bionic technology. When treating amputees daily, however, Brandt said that the ability to customize their prostheses through the use of scanner technology has fundamentally changed his ability to provide precise-fitting and comfortable prostheses to his patients. Scanner technology allows Brandt to take digital images of a patient’s residual limb for the mold, which he can then modify with software.

“Our field has never been standardized,” said Brandt. “But now you can be very accurate about where you want modifications. Fifty years ago you had guys that were true craftsmen and could take a block of willow wood and carve a leg out of it. With technology, you can actually help the patient heal now.”

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