Assessing the Relative Contributions of Active Ankle and Knee Assistance to the Walking Mechanics of Transfemoral Amputees Using a Powered Prosthesis.

Kimberly A Ingraham,Nicholas P Fey,Ann M Simon,Levi J Hargrove,Long Wang

doi:10.1371/journal.pone.0147661

Kimberly A Ingraham, Nicholas P Fey + Show 3 more

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https://doi.org/10.1371/journal.pone.0147661

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Journal: PloS one	Publication Date: Jan 25, 2016
Citations: 37	License type: CC BY 4.0

Affiliation: Shirley Ryan AbilityLab, Northwestern University

Abstract

Powered knee-ankle prostheses are capable of providing net-positive mechanical energy to amputees. Yet, there are limitless ways to deliver this energy throughout the gait cycle. It remains largely unknown how different combinations of active knee and ankle assistance affect the walking mechanics of transfemoral amputees. This study assessed the relative contributions of stance phase knee swing initiation, increasing ankle stiffness and powered plantarflexion as three unilateral transfemoral amputees walked overground at their self-selected walking speed. Five combinations of knee and ankle conditions were evaluated regarding the kinematics and kinetics of the amputated and intact legs using repeated measures analyses of variance. We found eliminating active knee swing initiation or powered plantarflexion was linked to increased compensations of the ipsilateral hip joint during the subsequent swing phase. The elimination of knee swing initiation or powered plantarflexion also led to reduced braking ground reaction forces of the amputated and intact legs, and influenced both sagittal and frontal plane loading of the intact knee joint. Gradually increasing prosthetic ankle stiffness influenced the shape of the prosthetic ankle plantarflexion moment, more closely mirroring the intact ankle moment. Increasing ankle stiffness also corresponded to increased prosthetic ankle power generation (despite a similar maximum stiffness value across conditions) and increased braking ground reaction forces of the amputated leg. These findings further our understanding of how to deliver assistance with powered knee-ankle prostheses and the compensations that occur when specific aspects of assistance are added/removed.

Highlights

The number of individuals with lower-limb amputations living in the U.S is projected to grow dramatically [1], and common clinical options for these individuals include mechanically-passive prosthetic knees and feet
Increasing ankle stiffness had a significant effect on stance time of the intact leg (p = 0.02), with a trend toward reduced stance time
Average posterior Ground reaction force (GRF) of the amputated leg was affected by increasing ankle stiffness (p = 0.023) and powered plantarflexion (p = 0.006; Fig 5)

Summary

Introduction

The number of individuals with lower-limb amputations living in the U.S is projected to grow dramatically [1], and common clinical options for these individuals include mechanically-passive prosthetic knees and feet. These devices provide swing phase resistance through friction, pneumatic and/or hydraulic mechanisms and normally lock during the stance phase of walking. Some of these systems are microprocessor-controlled, which can regulate their passive mechanics using more complex control architectures. When an individual receives a transfemoral amputation, the loss or physical modification of these muscles presents a significant and challenging task of replacing these biological characteristics with non-biological prosthetic systems

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