Assessing Design Trade-Offs in an Orthosis with Enhanced Functionality and Customizability

Ankle-foot orthoses (AFOs) commonly prescribed for balance disorders, weakness, and neurological deficits have limited functionality due to their static nature. They restrict the joint’s range of motion and hamper energy transfer, despite their success in mitigating foot drop. Foot drop is a condition that increases the risk of gait abnormalities and falls. To address the limitations of AFOs, this project seeks to improve the upon a Variable Stiffness Orthosis (VSO) design by incorporating a unique cam-based transmission that allows for decoupled energy storage and return.

The Decoupled Energy Storage and Return Variable Stiffness Orthosis (DESR-VSO) transmission has two cams which can be engaged during different phases of walking to provide both variable stiffness and energy recycling. Energy recycling is the phenomenon where energy is captured upon heel strike and returned during the push-off phase of gait. This proposal includes designing multiple versions of the cam-based transmission to optimize the balance between foot drop prevention (dorsiflexion assistance) and energy recycling. The transmission designs will be tested on the bench top and evaluated on patients with foot drop from peroneal nerve damage.

The testing and evaluation stage will guide the selection of the most promising transmission design for a future clinical trial. This project aligns with the Neurobionics Lab’s goal to enhance mobility for individuals with disabilities through device design and evaluation. Led by candidate Emily Bywater and Prof. Elliott Rouse at the University of Michigan, the research will benefit from the expertise of additional assistive device specialists and clinical advisors who have volunteered to collaborate.

The outcomes will offer insights into the impact of design decisions on energy recycling and foot drop mechanics, facilitating the selection of an optimal cam-based transmission. Feedback from clinicians and patients will contribute to future design improvements, while subsequent clinical trials will assess the effects of dorsiflexion assistance on patient gait and explore metrics for assessing how the device can be individualized. Emily’s training plan includes training in design, control theory, software engineering, biomechanics, professional development, and scientific communication. The project will be conducted in the state-of-the-art Rehabilitation Lab in the Ford Motor Company Robotics Building at the University of Michigan, where all of the necessary equipment for human subject studies, benchtop testing, and device fabrication is already established.

Grant Number: 5F31HD115309-03
NIH Institute/Center: NIH
Principal Investigator: Emily Bywater