Instantaneous stiffness and hysteresis of dynamic elastic response prosthetic feet

Webber, Christina M.; Kaufman, Kenton R.

doi:10.1177/0309364616683980

Cited by 22 publications

(38 citation statements)

References 30 publications

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“…20,21 Stiffness and ESR characteristics, including hysteresis effects, are important properties that have been tested for different dorsi/plantar-flexed positions to simulate prosthetic foot behavior in normal gait. [22][23][24][25] It has also been shown that mechanical functions of prosthetic feet can be altered by footwear. 22,26 Another important parameter, which can be emulated using mechanical testing, is the roll-over shape and therefore the course of the center of pressure (COP) beneath the foot during loading.…”

Section: Introductionmentioning

confidence: 99%

Characterizing adaptations of prosthetic feet in the frontal plane

Ernst

Altenburg

Schmalz

2020

Prosthetics &Amp; Orthotics International

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Background: Energy-storage and return feet incorporate various design features including split toes. As a potential improvement, an energy-storage and return foot with a dedicated ankle joint was recently introduced allowing for easily accessible inversion/eversion movement. However, the adaptability of energy-storage and return feet to uneven ground and the effects on biomechanical and clinical parameters have not been investigated in detail. Objectives: To investigate the design-related ability of prosthetic feet to adapt to cross slopes and derive a theoretical model. Study design: Mechanical testing and characterization. Methods: Mechanical adaptation to cross slopes was investigated for six prosthetic feet measured by a motion capture system. A theoretical model linking the measured data with adaptations is proposed. Results: The type and degree of adaptation depends on the foot design, for example, stiffness, split toe or continuous carbon forefoot, and additional ankle joint. The model used shows high correlations with the measured data for all feet. Conclusions: The ability of prosthetic feet to adapt to uneven ground is design-dependent. The split-toe feet adapted better to cross slopes than those with continuous carbon forefeet. Joints enhance this further by allowing for additional inversion and eversion. The influence on biomechanical and clinical parameters should be assessed in future studies. Clinical relevance Knowing foot-specific ability to adapt to uneven ground may help in selecting an appropriate prosthetic foot for persons with a lower limb amputation. Faster and more comprehensive adaptations to uneven ground may lower the need for compensations and therefore increase user safety.

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Section: Introductionmentioning

confidence: 99%

Characterizing adaptations of prosthetic feet in the frontal plane

Ernst

Altenburg

Schmalz

2020

Prosthetics &Amp; Orthotics International

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“…Both stiffness 13–17 and energy storage and return 18–20 properties have been shown to have a significant influence on amputee gait. As a result, a number of studies have attempted to quantify prosthetic foot stiffness 21–25 or energy storage properties. 21–28 These studies often make measurements for a few conditions: loading either the prosthetic heel to simulate heel strike or the forefoot keel to simulate toe off.…”

Section: Introductionmentioning

confidence: 99%

Stiffness and energy storage characteristics of energy storage and return prosthetic feet

Womac

Neptune

Klute

2019

Prosthetics &Amp; Orthotics International

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Background: Mechanical properties of prosthetic feet can significantly influence amputee gait, but how they vary with respect to limb loading and orientation is infrequently reported. Objective: The objective of this study is to measure stiffness and energy storage characteristics of prosthetic feet across limb loading and a range of orientations experienced in typical gait. Study design: This study included mechanical testing. Methods: Force–displacement data were collected at combinations of 15 sagittal and 5 coronal orientations and used to calculate stiffness and energy storage across prosthetic feet, stiffness categories, and heel wedge conditions. Results: Stiffness and energy storage were highly non-linear in both the sagittal and coronal planes. Across all prosthetic feet, stiffness decreased with greater heel, forefoot, medial, and lateral orientations, while energy storage increased with forefoot, medial, and lateral loading orientations. Stiffness category was proportional to stiffness and inversely proportional to energy storage. Heel wedge effects were prosthetic foot dependent. Conclusion: Orientation, manufacturer, stiffness category, and heel wedge inclusion greatly influenced stiffness and energy storage characteristics. Clinical relevance These results and an available graphical user interface tool may help improve clinical prescriptions by providing prosthetists with quantitative measures to compare prosthetic feet.

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“… 1 While the exact mechanics of ESR prosthetic feet are complex, a common, simplified model consists of a solid foot attached to the shank via a rotational spring, articulating around an estimated ankle axis. Damping is present to varying degrees, but elasticity (stiffness) dominates the mechanics; for example, in ESR feet without a shock absorber (i.e., no damping), only 5–15% of the energy stored is lost [ 30 ]. …”

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confidence: 99%

Amputee perception of prosthetic ankle stiffness during locomotion

Shepherd

Azocar

Major

et al. 2018

J NeuroEngineering Rehabil

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BackgroundProsthetic feet are spring-like, and their stiffness critically affects the wearer’s stability, comfort, and energetic cost of walking. Despite the importance of stiffness in ambulation, the prescription process often entails testing a limited number of prostheses, which may result in patients receiving a foot with suboptimal mechanics. To understand the resolution with which prostheses should be individually optimized, we sought to characterize below-knee prosthesis users’ psychophysical sensitivity to prosthesis stiffness.MethodsWe used a novel variable-stiffness ankle prosthesis to measure the repeatability of user-selected preferred stiffness, and implemented a psychophysical experiment to characterize the just noticeable difference of stiffness during locomotion.ResultsAll eight subjects with below-knee amputation exhibited high repeatability in selecting their Preferred Stiffness (mean coefficient of variation: 14.2 ± 1.7%) and were able to correctly identify a 7.7 ± 1.3% change in ankle stiffness (with 75% accuracy).ConclusionsThis high sensitivity suggests prosthetic foot stiffness should be tuned with a high degree of precision on an individual basis. These results also highlight the need for a pairing of new robotic prescription tools and mechanical characterizations of prosthetic feet.

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Instantaneous stiffness and hysteresis of dynamic elastic response prosthetic feet

Cited by 22 publications

References 30 publications

Characterizing adaptations of prosthetic feet in the frontal plane

Characterizing adaptations of prosthetic feet in the frontal plane

Stiffness and energy storage characteristics of energy storage and return prosthetic feet

Amputee perception of prosthetic ankle stiffness during locomotion

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