Design and clinical implementation of an open-source bionic leg

Ann M. Simon,Alejandro F. Azocar,Levi J. Hargrove,Elliott J. Rouse,Luke M. Mooney,Jean-François Duval

doi:10.1038/s41551-020-00619-3

Ann M. Simon, Alejandro F. Azocar + Show 4 more

Open Access

https://doi.org/10.1038/s41551-020-00619-3

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Abstract

In individuals with lower-limb amputations, robotic prostheses can increase walking speed, and reduce energy use, the incidence of falls and the development of secondary complications. However, safe and reliable prosthetic-limb control strategies for robust ambulation in real-world settings remain out of reach, partly because control strategies have been tested with different robotic hardware in constrained laboratory settings. Here, we report the design and clinical implementation of an integrated robotic knee–ankle prosthesis that facilitates the 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. We characterized the electromechanical and thermal performance of the bionic leg in benchtop testing, as well as its kinematics and kinetics in three individuals during walking on level ground, ramps and stairs. The open-source integrated-hardware solution and benchmark data that we provide should help with research and clinical testing of knee–ankle prostheses in real-world environments.

Highlights

In individuals with lower-limb amputations, robotic prostheses can increase walking speed, and reduce energy use, the incidence of falls and the development of secondary complications
This study describes the design, implementation and characterization of an open-source robotic knee–ankle prosthesis, and demonstrates control with three participants with transfemoral amputations ambulating with the leg on level ground, ramps and stairs
Through the Open Source Leg (OSL), we hope to reduce the amount of time and resources that are needed to pursue prosthetics research, enable fair comparison between different control systems and provide long-term multi-study technology to accelerate progress in the field of powered prosthetic legs

Summary

Introduction

In individuals with lower-limb amputations, robotic prostheses can increase walking speed, and reduce energy use, the incidence of falls and the development of secondary complications. Several research groups are developing powered knee[14,15], ankle[16,17,18,19] and knee–ankle (whole leg)[20,21,22] prostheses that have the ability to produce able-bodied kinematics and kinetics that are not possible, or are extremely difficult, with passive systems[23,24,25] These capabilities are typically achieved using electric motors that add net-positive mechanical energy analogous to the muscles within the leg. Some individual experiments show patients walking faster, using less metabolic energy or exhibiting improved centre-of-pressure progression, there has been discussion about the applicability of these systems in clinical settings or for people with lower activity levels[28] This is not necessarily a limitation of the prosthesis hardware but, rather, a lack of understanding about how best to control these devices. Despite promising research, key challenges remain in the development of control strategies that are safe, robust and intuitive

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