Quantifying Locomotor Outcomes with Agonist-Antagonist Myoneural Interface

Project Summary
An innovative new surgical technique - the agonist-antagonist myoneural interface (AMI) - restores
agonist-antagonist muscle dynamics in the residual limb to promote improvements in residual limb function
after lower limb loss. Disregarding the dynamic coupling of agonist-antagonist muscle pairs during traditional
amputation eliminates the natural contraction-relaxation dynamics of coupled muscles that sends sensory
information about limb speed and position to the brain. This lack of information results in decreased
proprioception and the ability to control a muscle-driven prosthesis. While this surgical technique is designed to
improve prosthesis control via electromyography (EMG) recordings in the residual limb, initial work suggests
that the benefits of AMI (e.g., increased prosthesis embodiment, residual limb volume) may extend to
conventional prostheses. However, the impacts of AMI on functional tasks such as walking or recovering
from walking perturbations when using a conventional prosthesis are unknown. We propose that the AMI
technique will increase the quality and quantity of sensory information received by the central nervous system,
improve the subsequent motor plan, and improve biomechanics during walking and perturbed walking with a
conventional prosthesis. Our central hypothesis is that by connecting agonist-antagonist muscles, the
suggested benefits of AMI will apply to use with conventional prostheses due to increased residual limb
proprioception and prosthesis embodiment. We will test our hypothesis through three specific aims. We will
prospectively compare locomotion mechanics in a cohort of persons with an AMI-amputation against those
with a traditional amputation using a measure of gait smoothness. We will also collect EMG data within the
residual limb during walking to assess residual limb muscle activations during walking as a means to validate the
scientific premise of AMI during walking with a conventional prosthesis. Second, we will evaluate the influence
of AMI on the response to perturbations during walking, simulating real-world trip or slip scenarios that have
fall-risk implications. Lastly, we will investigate the influence of self-reported prosthesis embodiment on
locomotion mechanics in each cohort to support our hypothesis that persons with AMI walk with improved
mechanics partly due to increased prosthesis embodiment. be related to greater gait smoothness and lesser
trunk angles and velocity during trip recovery. The proposed experiments will provide preliminary evidence of
AMI’s ability to improve locomotion mechanics, tripping recovery, and the influence of prosthesis embodiment
on locomotion with a conventional prosthesis. Findings will determine near-term, pragmatic benefits to AMI
amputation in patients who do not have access to a specialized neuroprosthesis.

Grant Number: 1R03HD114176-01
NIH Institute/Center: NIH
Principal Investigator: Courtney Butowicz