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Rogers-Bradley E, Yeon SH, Landis C, Lee DRC, Herr HM. Variable-stiffness prosthesis improves biomechanics of walking across speeds compared to a passive device. Sci Rep 2024; 14:16521. [PMID: 39019986 PMCID: PMC11255255 DOI: 10.1038/s41598-024-67230-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2024] [Accepted: 07/09/2024] [Indexed: 07/19/2024] Open
Abstract
Ankle push-off power plays an important role in healthy walking, contributing to center-of-mass acceleration, swing leg dynamics, and accounting for 45% of total leg power. The majority of existing passive energy storage and return prostheses for people with below-knee (transtibial) amputation are stiffer than the biological ankle, particularly at slower walking speeds. Additionally, passive devices provide insufficient levels of energy return and push-off power, negatively impacting biomechanics of gait. Here, we present a clinical study evaluating the kinematics and kinetics of walking with a microprocessor-controlled, variable-stiffness ankle-foot prosthesis (945 g) compared to a standard low-mass passive prosthesis (Ottobock Taleo, 463 g) with 7 study participants having unilateral transtibial amputation. By modulating prosthesis stiffness under computer control across walking speeds, we demonstrate that there exists a stiffness that increases prosthetic-side energy return, peak power, and center-of-mass push-off work, and decreases contralateral limb peak ground reaction force compared to the standard passive prosthesis across all evaluated walking speeds. We demonstrate a significant increase in center-of-mass push-off work of 26.1%, 26.2%, 29.6% and 29.9% at 0.75 m/s, 1.0 m/s, 1.25 m/s, and 1.5 m/s, respectively, and a significant decrease in contralateral limb ground reaction force of 3.1%, 3.9%, and 3.2% at 1.0 m/s, 1.25 m/s, and 1.5 m/s, respectively. This study demonstrates the potential for a quasi-passive microprocessor-controlled variable-stiffness prosthesis to increase push-off power and energy return during gait at a range of walking speeds compared to a passive device of a fixed stiffness.
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Affiliation(s)
- Emily Rogers-Bradley
- K. Lisa Yang Center for Bionics, Massachusetts Institute of Technology, Cambridge, 02139, USA
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, 02139, USA
- Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, T2N 1N4, Canada
| | - Seong Ho Yeon
- K. Lisa Yang Center for Bionics, Massachusetts Institute of Technology, Cambridge, 02139, USA
- Media Lab, Massachusetts Institute of Technology, Cambridge, 02142, USA
| | - Christian Landis
- K. Lisa Yang Center for Bionics, Massachusetts Institute of Technology, Cambridge, 02139, USA
- Media Lab, Massachusetts Institute of Technology, Cambridge, 02142, USA
| | - Duncan R C Lee
- K. Lisa Yang Center for Bionics, Massachusetts Institute of Technology, Cambridge, 02139, USA
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, 02139, USA
| | - Hugh M Herr
- K. Lisa Yang Center for Bionics, Massachusetts Institute of Technology, Cambridge, 02139, USA.
- Media Lab, Massachusetts Institute of Technology, Cambridge, 02142, USA.
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Molitor SL, Neptune RR. Lower-limb joint quasi-stiffness in the frontal and sagittal planes during walking at different step widths. J Biomech 2024; 162:111897. [PMID: 38103312 DOI: 10.1016/j.jbiomech.2023.111897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 11/28/2023] [Accepted: 12/04/2023] [Indexed: 12/19/2023]
Abstract
Quasi-stiffness describes the intersegmental joint moment-angle relationship throughout the progression of a task. Previous work has explored sagittal-plane ankle quasi-stiffness and its application for the development of powered lower-limb assistive devices. However, frontal-plane quasi-stiffness remains largely unexplored but has important implications for the development of exoskeletons since clinical populations often walk with wider steps and rely on frontal-plane balance recovery strategies at the hip and ankle. This study aimed to characterize frontal-plane hip and ankle quasi-stiffness during walking and determine how step width affects quasi-stiffness in both the frontal and sagittal planes. Kinematic and kinetic data were collected and quasi-stiffness values computed for healthy young adults (n = 15) during treadmill walking across a range of step widths. We identified specific subphases of the gait cycle that exhibit linear and quadratic frontal-plane quasi-stiffness approximations for the hip and ankle, respectively. In addition, we found that at wider step widths, sagittal-plane ankle quasi-stiffness increased during early stance (∼12-35% gait cycle), sagittal-plane hip quasi-stiffness decreased in late stance (∼40-55% gait cycle) and frontal-plane hip quasi-stiffness decreased during terminal stance (∼48-65% gait cycle). These results provide a framework for further exploration of frontal-plane quasi-stiffness, lend insight into how quasi-stiffness may relate to balance control at various step widths, and motivate the development of stiffness-modulating assistive devices to improve balance related outcomes.
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Affiliation(s)
- Stephanie L Molitor
- Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Richard R Neptune
- Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, USA.
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Hinton EH, Likens A, Hsiao HY, Binder-Markey BI, Binder-Macleod SA, Knarr BA. Ankle stiffness modulation during different gait speeds in individuals post-stroke. Clin Biomech (Bristol, Avon) 2022; 99:105761. [PMID: 36099707 DOI: 10.1016/j.clinbiomech.2022.105761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 09/01/2022] [Accepted: 09/05/2022] [Indexed: 02/07/2023]
Abstract
BACKGROUND Neurotypical individuals alter their ankle joint quasi-stiffness in response to changing walking speed; however, for individuals post-stroke, the ability to alter their ankle quasi-stiffness is unknown. Individuals post-stroke commonly have weak plantarflexor muscles, which may limit their ability to alter ankle quasi-stiffness. The objective was to investigate the relationship between ankle quasi-stiffness and propulsion, at two walking speeds. We hypothesized that in individuals post-stroke, there would be no difference in their paretic ankle quasi-stiffness between walking at a self-selected versus a fast speed. However, we hypothesized that ankle quasi-stiffness would correlate with gait speed and propulsion across individuals. METHODS Twenty-eight participants with chronic stroke walked on an instrumented treadmill at their self-selected and fast-walking speeds. Multilevel models were used to determine the relationships between ankle quasi-stiffness, speed, and propulsion. FINDINGS Overall, ankle quasi-stiffness did not increase within individuals from a self-selected to a fast gait speed (p = 0.69). A 1 m/s increase in speed across participants predicted an increase in overall ankle quasi-stiffness of 0.02 Nm/deg./kg (p = 0.03) and a 1 N/BW change in overall propulsion across participants predicted a 0.265 Nm/deg./kg increase in overall ankle quasi-stiffness (p < 0.0001). INTERPRETATION Individuals post-stroke did not modulate their ankle quasi-stiffness with increased speed, but across individuals there was a positive relationship between ankle quasi-stiffness and both speed and peak propulsion. Walking speed and propulsion are limited in individuals post-stroke, therefore, improving either could lead to a higher functional status. Understanding post-stroke ankle stiffness may be important in the design of therapeutic interventions and exoskeletons, where these devices augment the biological ankle quasi-stiffness to improve walking performance.
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Affiliation(s)
| | | | - Hao-Yuan Hsiao
- Department of Kinesiology and Health Education, University of Texas at Austin, Austin, TX, USA
| | - Benjamin I Binder-Markey
- Department of Physical Therapy and Rehabilitation Sciences and School of Biomedical Engineering, Sciences, and Health Systems, Drexel University, Philadelphia, PA, USA
| | - Stuart A Binder-Macleod
- Department of Physical Therapy, University of Delaware, Newark, DE, USA; Division of Physical Therapy, Emory University, Atlanta, GA, USA
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MacLean MK, Ferris DP. Effects of simulated reduced gravity and walking speed on ankle, knee, and hip quasi-stiffness in overground walking. PLoS One 2022; 17:e0271927. [PMID: 35944021 PMCID: PMC9362947 DOI: 10.1371/journal.pone.0271927] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 07/10/2022] [Indexed: 12/04/2022] Open
Abstract
Quasi-stiffness characterizes the dynamics of a joint in specific sections of stance-phase and is used in the design of wearable devices to assist walking. We sought to investigate the effect of simulated reduced gravity and walking speed on quasi-stiffness of the hip, knee, and ankle in overground walking. 12 participants walked at 0.4, 0.8, 1.2, and 1.6 m/s in 1, 0.76, 0.54, and 0.31 gravity. We defined 11 delimiting points in stance phase (4 each for the ankle and hip, 3 for the knee) and calculated the quasi-stiffness for 4 phases for both the hip and ankle, and 2 phases for the knee. The R2 value quantified the suitability of the quasi-stiffness models. We found gravity level had a significant effect on 6 phases of quasi-stiffness, while speed significantly affected the quasi-stiffness in 5 phases. We concluded that the intrinsic muscle-tendon unit stiffness was the biggest determinant of quasi-stiffness. Speed had a significant effect on the R2 of all phases of quasi-stiffness. Slow walking (0.4 m/s) was the least accurately modelled walking speed. Our findings showed adaptions in gait strategy when relative power and strength of the joints were increased in low gravity, which has implications for prosthesis and exoskeleton design.
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Affiliation(s)
- Mhairi K. MacLean
- Department of Biomechanical Engineering, University of Twente, Enschede, The Netherlands
- * E-mail:
| | - Daniel P. Ferris
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida, United States of America
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Maun JA, Gard SA, Major MJ, Takahashi KZ. Reducing stiffness of shock-absorbing pylon amplifies prosthesis energy loss and redistributes joint mechanical work during walking. J Neuroeng Rehabil 2021; 18:143. [PMID: 34548080 PMCID: PMC8456590 DOI: 10.1186/s12984-021-00939-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 09/08/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND A shock-absorbing pylon (SAP) is a modular prosthetic component designed to attenuate impact forces, which unlike traditional pylons that are rigid, can compress to absorb, return, or dissipate energy. Previous studies found that walking with a SAP improved lower-limb prosthesis users' comfort and residual limb pain. While longitudinal stiffness of a SAP has been shown to affect gait kinematics, kinetics, and work done by the entire lower limb, the energetic contributions from the prosthesis and the intact joints have not been examined. The purpose of this study was to determine the effects of SAP stiffness and walking speed on the mechanical work contributions of the prosthesis (i.e., all components distal to socket), knee, and hip in individuals with a transtibial amputation. METHODS Twelve participants with unilateral transtibial amputation walked overground at their customary (1.22 ± 0.18 ms-1) and fast speeds (1.53 ± 0.29 ms-1) under four different levels of SAP stiffness. Power and mechanical work profiles of the leg joints and components distal to the socket were quantified. The effects of SAP stiffness and walking speed on positive and negative work were analyzed using two-factor (stiffness and speed) repeated-measure ANOVAs (α = 0.05). RESULTS Faster walking significantly increased mechanical work from the SAP-integrated prosthesis (p < 0.001). Reducing SAP stiffness increased the magnitude of prosthesis negative work (energy absorption) during early stance (p = 0.045) by as much as 0.027 Jkg-1, without affecting the positive work (energy return) during late stance (p = 0.159), suggesting a damping effect. This energy loss was partially offset by an increase in residual hip positive work (as much as 0.012 Jkg-1) during late stance (p = 0.045). Reducing SAP stiffness also reduced the magnitude of negative work on the contralateral sound limb during early stance by 11-17% (p = 0.001). CONCLUSIONS Reducing SAP stiffness and faster walking amplified the prostheses damping effect, which redistributed the mechanical work, both in magnitude and timing, within the residual joints and sound limb. With its capacity to absorb and dissipate energy, future studies are warranted to determine whether SAPs can provide additional user benefit for locomotor tasks that require greater attenuation of impact forces (e.g., load carriage) or energy dissipation (e.g., downhill walking).
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Affiliation(s)
- Jenny Anne Maun
- Department of Biomechanics, University of Nebraska at Omaha, Omaha, NE, USA
| | - Steven A Gard
- Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA.,Jesse Brown VA Medical Center, Chicago, IL, USA
| | - Matthew J Major
- Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA.,Jesse Brown VA Medical Center, Chicago, IL, USA
| | - Kota Z Takahashi
- Department of Biomechanics, University of Nebraska at Omaha, Omaha, NE, USA.
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Clites TR, Shepherd MK, Ingraham KA, Wontorcik L, Rouse EJ. Understanding patient preference in prosthetic ankle stiffness. J Neuroeng Rehabil 2021; 18:128. [PMID: 34433472 PMCID: PMC8390224 DOI: 10.1186/s12984-021-00916-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 07/21/2021] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND User preference has the potential to facilitate the design, control, and prescription of prostheses, but we do not yet understand which physiological factors drive preference, or if preference is associated with clinical benefits. METHODS Subjects with unilateral below-knee amputation walked on a custom variable-stiffness prosthetic ankle and manipulated a dial to determine their preferred prosthetic ankle stiffness at three walking speeds. We evaluated anthropomorphic, metabolic, biomechanical, and performance-based descriptors at stiffness levels surrounding each subject's preferred stiffness. RESULTS Subjects preferred lower stiffness values at their self-selected treadmill walking speed, and elected to walk faster overground with ankle stiffness at or above their preferred stiffness. Preferred stiffness maximized the kinematic symmetry between prosthetic and unaffected joints, but was not significantly correlated with body mass or metabolic rate. CONCLUSION These results imply that some physiological factors are weighted more heavily when determining preferred stiffness, and that preference may be associated with clinically relevant improvements in gait.
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Affiliation(s)
- Tyler R Clites
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
- Robotics Institute, University of Michigan, Ann Arbor, MI, 48109, USA
- Neurobionics Lab, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Max K Shepherd
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208, USA
- Shirley Ryan Ability Lab, Chicago, IL, 60611, USA
- Neurobionics Lab, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Kimberly A Ingraham
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
- Robotics Institute, University of Michigan, Ann Arbor, MI, 48109, USA
- Neurobionics Lab, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Leslie Wontorcik
- Department of Physical Medicine and Rehabilitation, Michigan Medicine, University of Michigan Orthotics and Prosthetics Center, Ann Arbor, MI, 48104, USA
| | - Elliott J Rouse
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA.
- Robotics Institute, University of Michigan, Ann Arbor, MI, 48109, USA.
- Neurobionics Lab, University of Michigan, Ann Arbor, MI, 48109, USA.
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Tryggvason H, Starker F, Armannsdottir AL, Lecomte C, Jonsdottir F. Speed Adaptable Prosthetic Foot: Concept Description, Prototyping and Initial User Testing. IEEE Trans Neural Syst Rehabil Eng 2020; 28:2978-2986. [PMID: 33151884 DOI: 10.1109/tnsre.2020.3036329] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This article presents a novel design of a prosthetic foot that features adaptable stiffness that changes according to the speed of ankle motion. The motivation is the natural graduation in stiffness of a biological ankle over a range of ambulation tasks. The device stiffness depends on rate of movement, ranging from a dissipating support at very slow walking speed, to efficient energy storage and return at normal walking speed. The objective here is to design a prosthetic foot that provides a compliant support for slow ambulation, without sacrificing the spring-like energy return beneficial in normal walking. The design is a modification of a commercially available foot and employs material properties to provide a change in stiffness. The velocity dependent properties of a non-Newtonian working fluid provide the rate adaptability. Material properties of components allow for a geometry shift that results in a coupling action, affecting the stiffness of the overall system. The function of an adaptive coupling was tested in linear motion. A prototype prosthetic foot was built, and the speed dependent stiffness measured mechanically. Furthermore, the prototype was tested by a user and body kinematics measured in gait analysis for varying walking speed, comparing the prototype to the original foot model (non-modified). Mechanical evaluation of stiffness shows increase in stiffness of about 60% over the test range and 10% increase between slow and normal walking speed in user testing.
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