The Effects of Exoskeleton Assisted Knee Extension on Lower-Extremity Gait Kinematics, Kinetics, and Muscle Activity in Children with Cerebral Palsy

Zachary F Lerner,Diane L Damiano,Thomas C Bulea

doi:10.1038/s41598-017-13554-2

Zachary F Lerner, Diane L Damiano + Show 1 more

Open Access

https://doi.org/10.1038/s41598-017-13554-2

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Abstract

Individuals with cerebral palsy often exhibit crouch gait, a debilitating and inefficient walking pattern marked by excessive knee flexion that worsens with age. To address the need for improved treatment, we sought to evaluate if providing external knee extension assistance could reduce the excessive burden placed on the knee extensor muscles as measured by knee moments. We evaluated a novel pediatric exoskeleton designed to provide appropriately-timed extensor torque to the knee joint during walking in a multi-week exploratory clinical study. Seven individuals (5–19 years) with mild-moderate crouch gait from cerebral palsy (GMFCS I-II) completed the study. For six participants, powered knee extension assistance favorably reduced the excessive stance-phase knee extensor moment present during crouch gait by a mean of 35% in early stance and 76% in late stance. Peak stance-phase knee and hip extension increased by 12° and 8°, respectively. Knee extensor muscle activity decreased slightly during exoskeleton-assisted walking compared to baseline, while knee flexor activity was elevated in some participants. These findings support the use of wearable exoskeletons for the management of crouch gait and provide insights into their future implementation.

Highlights

Research utilizing gait analysis and musculoskeletal modeling suggests that the flexed posture during crouch gait reduces the capacity of the hip and knee extensor muscles to extend the lower-extremity joints during stance[21]
Our primary hypothesis was that providing additional extensor torque to the knee joint during the stance phase of crouch gait would result in improved knee extension and reduced knee extensor moments
Our findings support the hypothesis that providing a knee extensor torque during stance would result in an increase in knee extension coupled with a decrease in the biological knee extensor moment

Summary

Introduction

Research utilizing gait analysis and musculoskeletal modeling suggests that the flexed posture during crouch gait reduces the capacity of the hip and knee extensor muscles to extend the lower-extremity joints during stance[21]. Crouch gait is associated with elevated knee extensor muscle forces and increased knee extensor moments[22], diminished contribution from the ankle plantar flexors, and the reliance of more proximally located muscles for forward progression[23,24] In theory, these findings suggest that treating crouch via robotic knee extension assistance may reduce the excessive burden placed on the knee extensor muscles, improve the ability of several lower-extremity muscles to transfer mechanical energy from the legs to the center of mass, make walking more efficient, and prolong walking ability[25]. Our primary hypothesis was that providing additional extensor torque to the knee joint during the stance phase of crouch gait would result in improved knee extension and reduced knee extensor moments To evaluate this hypothesis, we implemented a novel pediatric exoskeleton in a 6-visit exploratory clinical study, collected motion capture, force plate, and electromyography measurements, and completed an inverse dynamics analysis

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