Helping Kids With Their Leaps and Bounds

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Advanced Biofidelic Lower Extremity Kids (ABLE Kids) Prosthesis Project aims to help kids hit the playground running.

Prosthetics manufacturers have traditionally shied away from the special challenges presented by the pediatric market. For technical as well as practical reasons, the needs of this patient population have been a tough sell in the boardroom. Some of these challenges result from the fact that kids move differently than adults do, and their gait patterns change dramatically as they progress along the requisite stages of growth and development. Contrast the wobbly gait of the rookie walker at one-year old with the more confident stride of the four-year-old, or the charging, hell-bent-for-leather gallop of children at ages six, nine, and 12. As a child grows, she experiences changes in her muscle control, balance, and confidence.


A significant hurdle for prosthetics designers has been to develop a system that is smart enough to accommodate a child's needs as she maneuvers along this developmental trajectory. The system must be intuitive, but also lightweight, compact, and powerful. Nascent technologies can adapt for the scale the pediatric population presents, offering space efficiency and necessary power without the addition of cumbersome weight. Orthocare Innovations, Oklahoma City, Oklahoma, is attempting to synthesize these existing technologies and tackle the unique design challenges presented by this small but demanding consumer population. Currently in development, the company's new pediatric ankle—the Advanced Biofidelic Lower Extremity Kids (ABLE Kids) prosthesis—will adapt to a child's needs as she matures.

Orthocare Innovations recently scored $183,234 in grant funds from the National Institutes of Health (NIH) for the project's Phase I exploratory trial. In competition with academic research institutions for the same funding pool, the company is uniquely positioned to bring ABLE Kids to market because its R&D is market-focused, according to Adam Arabian, PhD, PE, the project's lead engineer. Arabian notes that while there is certainly a value in purity of research, "there is also a reality that if you actually want to help people, you can't spend the next ten years, to turn the phrase, ‘polishing the cannonball.' At some point you've got to say…we have a great thing that can make people's lives better right now, and we just have to figure out a way to get it into people's hands."

While Arabian is hesitant to nail down a project timeline and suggests the launch for ABLE Kids may be many years out, he comments, "We are already in preliminary testing and gaining data and going through design revisions to make…a better product."

Arabian explains that great engineering is not typically borne of the "eureka" moment of brand new laboratory research, but rather is built on a synthesis of existing innovations that are put together in novel ways. The technological wherewithal that serves as the foundation for ABLE Kids is Orthocare Innovations' Smart Pyramid™. Introduced in 2009, this data-driven technology measures, documents, and optimizes socket forces in lower-limb prostheses. Since its launch, Smart Pyramid has acquired warehouses of data that feed into the ABLE Kids' "adaptive" mechanism, or what Arabian refers to as the system's control algorithm, which is fundamental to its design. The normal human ankle, he explains, is predictive: "Your proprioception, your eyes, everything about your environment tells you how to plan for what's coming up." Contrast this biological programming with powers intrinsic to a prosthesis. "Even a smart one," Arabian continues, "is inherently reactive—it's always taking into account what's going on right now." But because of improved microprocessor speeds and data streams taken from Smart Pyramid that look at real-time gait patterns, "we are able to very quickly determine what is going on in the child's surroundings—are they running or walking, on hills or flat, playing outside or sitting in class," he explains. "Each of those and many, many more situations demand slightly different configurations for the prosthesis to optimize the gait and minimize energy expenditure."

The aim is to take this complex set of inputs and control for them in a natural way without any conscious activity on the part of the child. One of the company's tenets is that any system must be smart enough to learn from the subject. A leg that feels clunky as the user shifts from the playground to the classroom, from running uphill to climbing stairs, or a system that requires a host of user interventions at each change in activity would be unworkable. Arabian comments, "If you [have to] click your heels together three times and say, ‘There's no place like home…' that's not natural, that's not something that somebody's going to enjoy." The sensation of moving between activities should feel as organic as possible. In the words of one of the company's founders, David Boone, PhD, MPH, CP, Arabian quotes, "‘You shouldn't feel it changing —it should just feel better.'"

In keeping with the space-efficiency demands of the product's intended end users, ABLE Kids will also build on the company's pioneering work in the miniaturization of hydraulic systems. Funded by Orthocare Innovations, researchers at Oak Ridge National Laboratory, Tennessee, have drawn on the science of mesofluidics to produce hydraulics with lines not much thicker than a pencil's graphite core that produce substantial power reliably and at a reasonable cost. These technologies, used in the ABLE Kids ankle, make sense for the pediatric population because they use the child's natural gait to produce motion, circumventing the need for a lot of power, and thereby reducing the problem of weight load, according to Arabian.

While Orthocare has the technological groundwork in place that can meet the size demands as well as the "organic" functionality that the company sets as its gold standard, the design must also accommodate the uniqueness of the pediatric gait. "Certain things…require substantial new ideas that make them go from an adult size to a child's size," Arabian says. "You can't simply make [components] smaller; they change as they are made smaller. That's just physics." He says that by the time a child becomes a teenager, she can tolerate an adult prosthesis fairly well. Younger children, however, present design challenges because their gait changes so dramatically over time. This will be the primary focus of the project's initial test phase, where the purpose "is to build and demonstrate an adaptive pediatric ankle," Arabian says. He cautions that the system "[will] almost certainly look nothing like a final product because there is so much left to learn, and you have to design for so many unknowns at the beginning." However, he adds that the result "will be a fully functional microprocessor-controlled pediatric ankle from which we will be able to understand the unique challenges of pediatric gait and how we can best move forward." Arabian underscores that Phase II funds are awarded to promising projects that have proven their viability. Such projects typically receive more grant funding than their Phase I predecessors.

Orthocare Innovations' eventual goal is to provide a full suite of microprocessor-controlled pediatric lower-limb components so that kids with limb loss or limb difference can hit the playground running.

Pam Martin can be reached at

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