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. 2014 Jun 10;9(6):e99387.
doi: 10.1371/journal.pone.0099387. eCollection 2014.

Configuring a powered knee and ankle prosthesis for transfemoral amputees within five specific ambulation modes

Ann M Simon  1 , Kimberly A Ingraham  2 , Nicholas P Fey  1 , Suzanne B Finucane  2 , Robert D Lipschutz  1 , Aaron J Young  3 , Levi J Hargrove  1
Affiliations

Configuring a powered knee and ankle prosthesis for transfemoral amputees within five specific ambulation modes

Ann M Simon et al. PLoS One. .

Abstract

Lower limb prostheses that can generate net positive mechanical work may restore more ambulation modes to amputees. However, configuration of these devices imposes an additional burden on clinicians relative to conventional prostheses; devices for transfemoral amputees that require configuration of both a knee and an ankle joint are especially challenging. In this paper, we present an approach to configuring such powered devices. We developed modified intrinsic control strategies--which mimic the behavior of biological joints, depend on instantaneous loads within the prosthesis, or set impedance based on values from previous states, as well as a set of starting configuration parameters. We developed tables that include a list of desired clinical gait kinematics and the parameter modifications necessary to alter them. Our approach was implemented for a powered knee and ankle prosthesis in five ambulation modes (level-ground walking, ramp ascent/descent, and stair ascent/descent). The strategies and set of starting configuration parameters were developed using data from three individuals with unilateral transfemoral amputations who had previous experience using the device; this approach was then tested on three novice unilateral transfemoral amputees. Only 17% of the total number of parameters (i.e., 24 of the 140) had to be independently adjusted for each novice user to achieve all five ambulation modes and the initial accommodation period (i.e., time to configure the device for all modes) was reduced by 56%, to 5 hours or less. This approach and subsequent reduction in configuration time may help translate powered prostheses into a viable clinical option where amputees can more quickly appreciate the benefits such devices can provide.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Diagram of finite state machine for level ground walking.
Figure 2
Figure 2. Users (A) walking, (B) ascending a ramp, and (C) climbing stairs using the powered prosthesis.
Figure 3
Figure 3. Average prosthetic knee and ankle joint kinematics and kinetics for each user.
Joint powers are normalized by the mass of the user wearing the powered prosthesis.
See this image and copyright information in PMC

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