iPed: One Step Closer to Human Function

The iPed has a full anatomical 70 degrees range of motion (ROM), and muscular replicating resistance characteristics throughout that range of motion, to provide appropriate movement independent of the ambulated environment. Photographs courtesy of Martin Bionics and College Park Industries. As Christopher Columbus discovered, the earth is not flat. Today, most of us take Columbus' discovery for granted, but for persons with lower-extremity limb loss or limb difference, navigating the varying terrain of our world is a daily challenge. Helping people with lower-limb amputations overcome this challenge was the impetus behind the development of the iPed, a robotic foot-ankle prosthesis that utilizes adaptive control algorithms to mimic the function of the anatomical ankle by providing real-time accommodation for force, speed, and terrain changes. The device, which is currently in prototype form, was developed by Jay Martin, CP, LP, founder and president of research and development at Martin Bionics, Oklahoma City, Oklahoma, a company that researches, designs, and commercializes advanced technology for the prosthetics industry. Martin, whose background is in clinical prosthetics and kinesiology, started pursuing advanced prosthetic design shortly after completing his education in a effort to understand "how to better mesh man and machine." He developed the initial concept behind the iPed while working as a clinical and research prosthetist at Scott Sabolich Prosthetics and Research, Oklahoma City. "I realized the technology that was commercially available was also a limiting factor in helping patients to be as functional as they could be," Martin says. "The [foot-ankle] prostheses available were not able to react to the varying terrains of the ambulating environment in the same manner as a biological ankle. My goal is to create technologies to enable amputees to not be limited by their prosthesis." Martin established Martin Bionics in 2002. In January 2007, he partnered with College Park Industries (CPI), Fraser, Michigan, to help complete the development of the device and commercialize it. Chris Johnson, director of engineering, product design, and testing at CPI, is the alpha tester of the iPed. Johnson lost his right leg below the knee as a result of train-pedestrian accident in 1982. According to Johnson, CPI was impressed not only by the technology that Martin Bionics is advancing but also by the ongoing progress the company was making on the iPed's development. "One tipping point was the simple realization of where the market is going," says Johnson. "Computer control is inevitable, and to get there CPI has to start the journey. Martin Bionics has credible technology, and the chemistry' was right between the two companies." Martin and Johnson previewed the third iPed prototype during the 2007 American Orthotic & Prosthetic Association (AOPA) National Assembly, held September 17-20 in Las Vegas, Nevada. Martin says that while there have been a couple of test subjects so far, Johnson has "really helped us push the limits of this technology. As a transtibial amputee, I'd say Chris is probably in the top percentile in terms of activity level. He lives on a ranch, where there's a lot of mountainous and sloped terrain. Watching him leap from boulder to boulder has been incredible." The iPed is a significant advancement from current mechanical systems, which "cannot replicate human movement in all environments," Martin says. "They are okay on level terrain and in controlled environments, but they cannot react dynamically to force and terrain changes. The next generation of feet needs to have intelligence built in to assess the environment and react accordingly. "Being able to accommodate for environmental factors will help nearly all amputees - from walking up ramps or stairs, or carrying heavy groceries, to soldiers who have undergone an amputation and wish to return to active duty with their prosthesis," Martin continues. "With the prosthesis having an intelligent control system and adaptive actuator, it is no longer as much the limiting factor in the amputee's functional abilities. The iPed system is capable of accurately replicating natural foot and ankle movement in all conditions, and in all environments." Unlike the most advanced computer-controlled foot currently available, which is capable of changing its angle during the swing phase of the gait cycle but is locked out in stance phase, the iPed features full muscular replication in stance and swing phases, which allows for real-time control of angle and resistance. "Our current ankle design uses computational intrinsic control (CIC) by taking input information from sensors within the device and sending that information to the microprocessor, which alters the actuator movement accordingly," says Martin. "As a user walks down a hill or picks up his or her child, the resistance, angular velocity, angle of resistance, timing, and other factors of the ankle biomechanics are altered in real time to provide natural movement, ease of use, symmetry, and safety. "You need real-time control of the prosthesis to match the user's intended movement," Martin continues. "It's a greater integration of the body with the prosthesis." The iPed is currently slated for a 2008 release, and Martin says there are plans for an extended patient trial once the iPed gets closer to commercialization. "We will be doing those through select facilities," he says. The development of the iPed has already far exceeded Martin's expectations. "We originally set out to achieve a computer-controlled foot. The capabilities have far exceeded the expectations in terms of how the foot reacts to force, speed, and terrain changes," he says. Johnson agrees. "The iPed differs radically in its range of motion (ROM) from conventional prosthetic feet," he says. "The wide range of terrain accommodation, such as walking up and down a hill with the foot following the terrain and the ability to sit with the foot in a relaxed, plantarflexed position, is truly remarkable to me." Karen Henry can be reached at karen@opedge.com . Editor's note: The O&P EDGE regularly reports on advances in O&P technology and does not promote or endorse individual companies or their products.

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