Tech Briefs

Precision measurements of motion capture technology are leading to the development of improved prostheses.

For veterans who have lost a limb, a prosthesis is a lifeline. An artificial device not only provides mobility and enables routine activity, it can be life giving — emotionally as well as physically.

A patient with bilateral prostheses uses live feedback from the Vicon system in the virtual environment to work on pelvic control and foot alignment with his VA physical therapist in the Advanced Prosthetics Lab of the Cleveland VA Medical Center. (Credit: Vicon)

Designing and manufacturing the most efficient and comfortable prostheses requires the collection of very accurate measurements and movement data. Two facilities located in different parts of the country are using Vicon motion capture technology to conduct groundbreaking research that is making a dramatic difference in the lives of amputees, many of them veterans.

Better, Faster, Stronger

At the Cleveland VA (Veterans Affairs) Medical Center, Elizabeth Hardin, Ph.D. and Matt Fleming, prosthesis fabricator and former Marine, make up a seasoned team that’s pushing the boundaries of life science research to help design and create better-performing prostheses. Motion capture technology is used extensively in the medical center’s Motion Study Lab and Advanced Prosthetics and V-Gait Lab, and is vital to their research with Dan Simon, professor of electrical engineering at Cleveland State University.

The two labs at the center have a total of 26 Vicon cameras in use, serving 12 research projects in addition to clinical outreach. While each lab collects motion and force data, one focuses more on the activities of daily living — including sitting, standing, and walking over ground using a 10-m walkway — while the other uses a force-measuring treadmill to collect data in a virtual environment, related to walking, jogging, and running at various speeds. According to Hardin, the setup in both labs has “fantastic resolution,” capturing 50, 14-mm markers over 10 m of motion with no marker dropout. But perhaps most important to the team is precision. Accuracy and valid measurements are critical to their research and to the data that drives the engineering and creation that is ushering a new age of prosthetic development.

Elizabeth Hardin (left) applies reflective markers to a patient with bilateral prostheses in the virtual reality system of the Advanced Prosthetics Lab while Amputee Coordinator, Joe Bonscer (right) checks the safety harness. (Credit: Vicon)

For Fleming, an amputee, his experience and intimate knowledge of the challenges faced by amputees is invaluable to his fabrication work. “I apply my day-to-day life experience to my work,” he says. “I know what I need my own prosthesis to do; it needs to serve a lot of complex functions, so that drives my work here at the lab.”

Improving on Biology?

VA research scientist and Assistant Professor Alena Grabowski is also doing groundbreaking work in her Applied Biomechanics Lab at the University of Colorado, Boulder. Here, a 10-camera Vicon motion capture system operates in a full 3D environment.

Two treadmills, both 3D force and speed measuring units, measure the forces exerted by the leg for different states of motion: walking, running, and sprinting up to nearly 30 miles per hour in the case of elite athletes.

Precision measurements are critical as the mechanics of the body change according to the gait. Further, analyzing how the movements of a prosthetic leg differ from a biological one is a fundamental part of the process. The Vicon system helps isolate each segment of the leg, which is essential to understanding how the body moves. The team is also working to develop quantitative algorithms to assess how prostheses function dynamically.

“Everybody wants a better functioning body,” says Grabowski. “It’s critical that we look at how the body moves and analyze each different segment.”

Motion capture technology is helping the lab excel within advanced bionics. Grabowski and her team are studying a powered ankle/foot prosthesis, a relatively new device on the market. They’re working to better understand the product and assess its function, testing, for example, its effectiveness in challenging situations such as on slopes as opposed to how it functions on flat ground. It’s all about the nuances and the goal is always ‘how can we make it more effective?’

Grabowski can imagine the day when technology helps the industry move to a new stage of prosthetic and assistive device performance. “People want high-functioning devices,” says Grabowski. To that end, she’s aiming high. “My hope is that we move to a point where we can create something that’s better than a biological leg. We have some great creative minds that can rethink and redesign what’s possible.”

The Road Ahead

Each lab is doing work that has far-reaching impact, improving the quality of life and independence of amputees. The capture of precise motion data is critical to this research. As cameras get smaller and more powerful and set-ups easier to install, more and more facilities around the world are advancing the development of prostheses. This accessibility and the results like those above will ensure that daily life for veterans and all those who have lost limbs will only improve.

For more information, visit