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A Battery-Powered Ankle Exoskeleton Improves Gait Mechanics in a Feasibility Study of Individuals with Cerebral Palsy

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Abstract

Neuromuscular impairment associated with cerebral palsy (CP) often leads to life-long walking deficits. Our goal was to evaluate the ability of a novel untethered wearable ankle exoskeleton to reduce the severity of gait pathology from CP. In this clinical feasibility study of five individuals with CP, we used instrumented gait analysis to quantify how powered plantar-flexor assistance affected gait mechanics following multi-visit acclimation. Compared to how each participant walked normally, walking with untethered exoskeleton assistance resulted in improved ankle plantar-flexion and knee extension; residual flexion deformity across the lower-extremity improved by a clinically significant 14.4° (p = 0.022). Powered plantar-flexor assistance increased average total positive ankle power by 44% (p = 0.037), and resulted in a 30% reduction in average negative biological ankle power (p = 0.004) and a 29% reduction in average positive hip power (p = 0.009). These findings suggest that powered ankle assistance augmented, rather than simply replaced, biological function to produce a more efficient gait pattern, which was corroborated by a 19% improvement in metabolic cost of transport (p = 0.011). This study provides evidence in support of the continued investigation of ankle assistance in mobility and rehabilitation interventions for this patient population.

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Acknowledgments

We thank Gian Maria Gasparri, Jason Luque, and Andrea Lerner for their critical assistance with this study. This study was supported in part by NIH Grant No. 1R03HD094583-01 and Arizona Department of Health Serves Grant No. ADHS18-198864.

Conflict of Interest

Z.F.L. is a named inventor on Provisional U.S. Patent Application No. 62/644,163, “Ankle Exoskeleton System and Method for Assisted Mobility and Rehabilitation” covering the exoskeleton used in the study.

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Authors and Affiliations

  1. Department of Mechanical Engineering, Northern Arizona University, 15600 S McConnell Drive, NAU EGR Bldg 69, Flagstaff, AZ, 86011, USA

    Zachary F. Lerner, Taryn A. Harvey & Jennifer L. Lawson

  2. Department of Orthopedics, University of Arizona College of Medicine, Phoenix, AZ, 85003, USA

    Zachary F. Lerner

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  1. Zachary F. Lerner
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  2. Taryn A. Harvey
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Correspondence to Zachary F. Lerner.

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Lerner, Z.F., Harvey, T.A. & Lawson, J.L. A Battery-Powered Ankle Exoskeleton Improves Gait Mechanics in a Feasibility Study of Individuals with Cerebral Palsy. Ann Biomed Eng 47, 1345–1356 (2019). https://doi.org/10.1007/s10439-019-02237-w

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