Open-source Prosthesis Available for Real-world Testing

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Photograph courtesy of Joseph Xu/Michigan Engineering.

A team of researchers published information about the design and clinical testing of an open-source lower-limb robotic prosthesis. They intend for the integrated-hardware solution and benchmark data to help with research and clinical testing of knee-ankle prostheses in real-world environments. The knee and ankle joints can work independently, so the device can facilitate testing among people with transfemoral or transtibial amputations. The prosthesis includes free-to-copy, step-by-step guides to help other researchers assemble it or order parts for it.

The difficulties in developing safe and reliable prosthetic-limb control strategies outside of a laboratory setting led to their development of the device, according to the study's authors.

"The challenge stems from the fact that these limbs support a person's body weight," Elliott Rouse, PhD, a biomedical engineer and director of the neurobionics lab at the University of Michigan told IEE Spectrum. "If it makes a mistake, a person can fall and get seriously injured. That's a really high burden on a control system, in addition to trying to have it help people with activities in their daily life."

To help overcome the challenges, Rouse and his team designed an integrated robotic knee-ankle prosthesis that can facilitate real-world testing of its biomechanics and control strategies. The bionic leg is open source; it includes software for low-level control and for communication with control systems, and its hardware design is customizable, enabling reduction in its mass and cost, improvement in its ease of use, and independent operation of the knee and ankle joints. The Open Source Leg prosthesis will prevent other researchers from having to develop their own devices for testing, which is expensive and time-consuming, or rely on virtual testing, which may not provide real-world results.

The study, Design and clinical implementation of an open-source bionic leg, published in Nature Biomedical Engineering, characterized the electromechanical and thermal performance of the bionic leg in benchtop testing, as well as its kinematics and kinetics in three people during walking on level ground, ramps, and stairs. Rouse said the testers were able to meet goals set by physical therapists and said the device felt supportive, responsive, and smooth.

The team also produced videos illustrating how to build and test the hardware and developed code for programming the prosthetic to walk using a preliminary control system. The Open Source Leg is relatively easy to assemble, control, and maintain.

Rouse told IEEE Spectrum that eight other institutions have asked for the new legs or are building their own. "We're really impressed with their interest and desire to collaborate with us and willingness to help," he said. "They're helping make the system better."

To learn more, visit Open Source Leg.