Choosing appropriate prosthetic ankle work to reduce the metabolic cost of individuals with transtibial amputation

Ingraham, Kimberly A.; Choi, Hwan; Gardinier, Emily S.; Remy, C. David; Gates, Deanna H.

doi:10.1038/s41598-018-33569-7

Cited by 23 publications

(19 citation statements)

References 44 publications

(58 reference statements)

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“…Ankle-foot work decreased by about 0.036 J/kg from the subject’s lowest stiffness to the highest stiffness, but this decrease only amounted to about a 3% decrease in metabolic cost. Previous studies that have modulated the amount of ankle work may suggest that a greater change in work may be needed to see a large change in metabolic energy [24, 31, 58]. Contrary to our findings, Caputo et al used a powered prosthesis and found that for a work decrease of about 0.03 J/kg, there would be an increase of about 0.148 W/kg in metabolic cost [31].…”

Section: Discussioncontrasting

confidence: 99%

“…The metabolic cost did decrease by about 7 to 8% from the highest to the medium stiffness, which had about a 2.6 J difference in push off work (0.035 J/kg for a 75 kg person) [24]. In a study with a commercially-available powered prosthesis, the prosthetist-chosen power setting was a mean ankle work of 0.11 ± 0.06 J/kg, but the best power setting for decreasing metabolic cost (by about 8.8% ± 4.6%) was 0.24 ± 0.07 J/kg [58]. Therefore, our differences in ankle-foot work between stiffness conditions may not have been large enough to influence the metabolic cost.…”

Section: Discussionmentioning

confidence: 99%

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The effects of ankle stiffness on mechanics and energetics of walking with added loads: a prosthetic emulator study

Hedrick

Malcolm

Wilken

et al. 2019

J NeuroEngineering Rehabil

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BackgroundThe human ankle joint has an influential role in the regulation of the mechanics and energetics of gait. The human ankle can modulate its joint ‘quasi-stiffness’ (ratio of plantarflexion moment to dorsiflexion displacement) in response to various locomotor tasks (e.g., load carriage). However, the direct effect of ankle stiffness on metabolic energy cost during various tasks is not fully understood. The purpose of this study was to determine how net metabolic energy cost was affected by ankle stiffness while walking under different force demands (i.e., with and without additional load).MethodsIndividuals simulated an amputation by using an immobilizer boot with a robotic ankle-foot prosthesis emulator. The prosthetic emulator was controlled to follow five ankle stiffness conditions, based on literature values of human ankle quasi-stiffness. Individuals walked with these five ankle stiffness settings, with and without carrying additional load of approximately 30% of body mass (i.e., ten total trials).ResultsWithin the range of stiffness we tested, the highest stiffness minimized metabolic cost for both load conditions, including a ~ 3% decrease in metabolic cost for an increase in stiffness of about 0.0480 Nm/deg/kg during normal (no load) walking. Furthermore, the highest stiffness produced the least amount of prosthetic ankle-foot positive work, with a difference of ~ 0.04 J/kg from the highest to lowest stiffness condition. Ipsilateral hip positive work did not significantly change across the no load condition but was minimized at the highest stiffness for the additional load conditions. For the additional load conditions, the hip work followed a similar trend as the metabolic cost, suggesting that reducing positive hip work can lower metabolic cost.ConclusionWhile ankle stiffness affected the metabolic cost for both load conditions, we found no significant interaction effect between stiffness and load. This may suggest that the importance of the human ankle’s ability to change stiffness during different load carrying tasks may not be driven to minimize metabolic cost. A prosthetic design that can modulate ankle stiffness when transitioning from one locomotor task to another could be valuable, but its importance likely involves factors beyond optimizing metabolic cost.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The effects of ankle stiffness on mechanics and energetics of walking with added loads: a prosthetic emulator study

Hedrick

Malcolm

Wilken

et al. 2019

J NeuroEngineering Rehabil

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“…Particularly in individuals with lower limb amputation, metabolic energy associated with walking is known to be much higher than the ablebodied population and powered prostheses are designed to reduce this burden on their users. (34,35) However, the current gold standard for measuring energy consumption is open-circuit spirometry which is a time-consuming process and requires a user to be tethered to a machine(36). While metabolic cost does play an important role in a person's gait quality, studies have shown that individuals may optimize their gait for a combination of metabolic cost and other factors (37), which could include stability, speed, comfort, or esthetics.…”

Section: Resultsmentioning

confidence: 99%

Identifying gait quality metrics sensitive to changes in lower limb constraint

Herrin

Kwak

Chang

2021

Preprint

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Background Manual tuning of robotic lower limb prostheses can be time consuming for both the patient and the clinician and requires in-person visits to a clinic. An automated process for the tuning parameters of a robotic lower limb prosthesis could result in a substantial savings in healthcare resources. A critical challenge to an automated parameter tuning algorithm is the quantification of a person’s gait quality. There is not good agreement in the literature of an objective outcome measure that can rapidly assess gait quality in lower limb amputees. As a first step, we investigated the ability of four common gait quality metrics to detect differences in gait quality: Prosthetic Observational Gait Score (POGS), Gait Deviation Index (GDI), Lateral Sway, and Impulse Asymmetry. Methods We systematically applied four unilateral lower limb joint constraint conditions (baseline/no constraint, ankle constraint, knee constraint, and knee + ankle constraint) to nine able-bodied participants walking at three different speeds (0.7, 0.85 and 1.0 m/s). We calculated and compared the resulting GDI, POGS, Lateral Sway and Impulse Asymmetry scores across all conditions. We performed a 2-way ANOVA statistical analysis to compare sensitivity of the metrics to the various conditions with significance defined by an alpha-level = 0.05. Results The Lateral Sway metric distinguished three joint constraint conditions and two of the speed conditions. Both GDI and POGS were able to distinguish four out of six possible constraint-speed conditions, while Impulse Asymmetry was only able to detect differences between three of the six constraint-speed conditions. Conclusions No single gait quality metric could distinguish every condition. Accordingly, a single metric of gait quality may be inadequate for tuning a prosthesis and therefore multiple metrics and sensors may provide the best results for tuning a prosthesis to the most natural gait pattern for an individual. Compared to the more complex gait measures, Lateral Sway performed well as a simple metric that might easily be operationalized into a real-time parameter tuning controller.

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“…This could be an argument for personalized controllers since prosthesis assistance is learned based on observed human-robot responses, which may resolve the problems that K3 ambulators have in learning to use a powered prosthesis. Another study found that, for all ten individuals with unilateral transtibial amputation included in the experimental protocol, the best tested power setting for the BiOM prosthesis (BiOM T2 Ankle, BionX Medical Technologies Inc., Cambridge, MA) was consistently higher than the prosthetist-chosen setting [13]. This resulted in a statistically significant difference in metabolic cost between the best tested and prosthetist-chosen power settings.…”

Section: Introductionmentioning

confidence: 99%

A Data-Driven and Personalized Symmetry Controller for Robotic Ankle-Foot Prostheses

Prasanna¹,

Realmuto²,

Anderson³

et al. 2022

Preprint

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<p>People with unilateral transtibial amputation generally exhibit asymmetric gait, likely due to inadequate prosthetic ankle function. This results in compensatory behavior, leading to long-term musculoskeletal impairments (e.g., osteoarthritis in the joints of the intact limb). Powered prostheses can better emulate biological ankles, however, control methods are over-reliant on able-bodied data, require extensive amounts of tuning by experts, and cannot adapt to each user’s unique gait patterns. This work directly addresses all these limitations with a personalized and data-driven control strategy. Our controller uses a virtual setpoint trajectory within an impedance-inspired formula to adjust the dynamics of the robotic ankle-foot prosthesis as a function of gait phase. A single sensor measuring thigh motion is used to estimate the gait phase in real time. The virtual setpoint trajectory is modified via a data-driven iterative learning strategy aimed at optimizing ankle kinematic symmetry. The controller was experimentally evaluated on two people with transtibial amputation. The control scheme successfully increased ankle angle symmetry about the two limbs by 25.3% when compared to the passive condition. In addition, the symmetry controller significantly increased peak prosthetic ankle power output at push-off by 0.52 W/kg and significantly reduced biomechanical risk factors associated with osteoarthritis in the intact limb. This research demonstrates the benefits of personalized and data-driven symmetry controllers for robotic ankle-foot prostheses. </p>

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Choosing appropriate prosthetic ankle work to reduce the metabolic cost of individuals with transtibial amputation

Cited by 23 publications

References 44 publications

The effects of ankle stiffness on mechanics and energetics of walking with added loads: a prosthetic emulator study

The effects of ankle stiffness on mechanics and energetics of walking with added loads: a prosthetic emulator study

Identifying gait quality metrics sensitive to changes in lower limb constraint

A Data-Driven and Personalized Symmetry Controller for Robotic Ankle-Foot Prostheses

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