scholarly journals A Computational Gait Model with a Below-Knee Amputation and a Semi-Active Variable-Stiffness Foot Prosthesis

2021 ◽  
Author(s):  
Michael McGeehan ◽  
Peter Adamczyk ◽  
Kieran Nichols ◽  
Michael E. Hahn
Keyword(s):  
Lower Limb ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Variable Stiffness ◽  
Contact Forces ◽  
Prosthesis Design ◽  
Limb Loss ◽  
Design Parameters ◽  
Knee Amputation ◽  
Musculoskeletal Models

Abstract Introduction: Simulations based on computational musculoskeletal models are powerful tools for evaluating effects of potential biomechanical interventions, such as implementing a novel prosthesis. However, the utility of simulations to evaluate effects of prosthesis design parameters on gait mechanics has not been fully realized due to lack of a readily-available limb loss-specific gait model and methods for efficiently modeling the energy storage and return dynamics of passive foot prostheses. The purpose of this study was to develop and validate a forward simulation-capable gait model with lower limb loss and a semi-active variable-stiffness foot (VSF) prosthesis. Methods: A seven-segment 28-DoF gait model was developed and forward kinematics simulations, in which experimentally-observed joint kinematics were applied and resulting foot contact forces evolved accordingly, were computed for four subjects with unilateral below-knee amputation walking with a VSF. Results: Model-predicted resultant ground reaction force (GRFR) matched well under trial-specific optimized parameter conditions (mean R2: 0.97, RMSE: 7.7% body weight (BW)) and unoptimized (subject-specific, not trial-specific) parameter conditions (mean R2: 0.93, RMSE: 12% BW). Simulated anterior-posterior center of pressure demonstrated mean R2 = 0.64 and RMSE = 14% foot length. Simulated kinematics remained consistent with input data (0.23 deg RMSE, R2 > 0.99) for all conditions. Conclusions: These methods may be useful for simulating gait of individuals with lower limb loss and predicting GRFR with novel VSF prostheses. Such data are useful to optimize user-specific prosthesis design parameters.

scholarly journals A computational gait model with a below-knee amputation and a semi-active variable-stiffness foot prosthesis

2021 ◽  
Author(s):  
Michael McGeehan
Keyword(s):  
Lower Limb ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Variable Stiffness ◽  
Contact Forces ◽  
Prosthesis Design ◽  
Limb Loss ◽  
Design Parameters ◽  
Knee Amputation ◽  
Musculoskeletal Models

Introduction: Simulations based on computational musculoskeletal models are powerful tools for evaluating the effects of potential biomechanical interventions, such as implementing a novel prosthesis. However, the utility of simulations to evaluate the effects of varied prosthesis design parameters on gait mechanics has not been fully realized due to lack of a readily-available limb loss-specific gait model and methods for efficiently modeling the energy storage and return dynamics of passive foot prostheses. The purpose of this study was to develop and validate a forward simulation-capable gait model with lower limb loss and a semi-active variable-stiffness foot (VSF) prosthesis. Methods: A seven-segment 28-DoF gait model was developed and forward kinematics simulations, in which experimentally-observed joint kinematics were applied and the resulting contact forces under the prosthesis evolved accordingly, were computed for four subjects with unilateral below-knee amputation walking with a VSF. Results: Model-predicted resultant ground reaction force (GRFR) matched well under trial-specific optimized parameter conditions (mean R2: 0.97, RMSE: 7.7% body weight (BW)) and unoptimized (subject-specific, but not trial-specific) parameter conditions (mean R2: 0.93, RMSE: 12% BW). Simulated anterior-posterior center of pressure demonstrated a mean R2 = 0.64 and RMSE = 14% foot length. Simulated kinematics remained consistent with input data (0.23 deg RMSE, R2 > 0.99) for all conditions. Conclusions: These methods may be useful for simulating gait among individuals with lower limb loss and predicting GRFR arising from gait with novel VSF prostheses. Such data are useful to optimize prosthesis design parameters on a user-specific basis.

scholarly journals A reduced order computational model of a semi-active variable-stiffness foot prosthesis

2020 ◽  
Author(s):  
Michael McGeehan ◽  
Peter Adamczyk ◽  
Kieran Nichols ◽  
Michael Hahn
Keyword(s):  
Body Weight ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Variable Stiffness ◽  
Performance Standard ◽  
Design Parameters ◽  
Compression Tests ◽  
Static Compression ◽  
Lumped Parameter ◽  
Contact Models

INTRODUCTION: Passive energy storage and return (ESR) feet are the current performance standard in lower limb prostheses. A recently developed semi-active variable-stiffness foot (VSF) prosthesis balances the simplicity of a passive ESR device with the adaptability of a powered design. The purpose of this study was to model and simulate the ESR properties of the VSF prosthesis. METHODS: The ESR properties of the VSF were modeled as a lumped parameter overhung beam. The overhung length is variable, allowing the model to exhibit variable ESR stiffness. Foot-ground contact was modeled using sphere-to-plane contact models. Contact parameters were optimized to represent the geometry and dynamics of the VSF and its foam base. Static compression tests and gait were simulated. Simulation outcomes were compared to corresponding experimental data. RESULTS: Stiffness of the model matched that of the physical VSF (R2: 0.98, RMSE: 1.37 N/mm). Model-predicted resultant ground reaction force (GRFR) matched well under optimized parameter conditions (R2: 0.98, RMSE: 5.3% body weight,) and unoptimized parameter conditions (R2: 0.90, mean RMSE: 13% body weight). Anterior-posterior center of pressure matched well with R2 > 0.94 and RMSE < 9.5% foot length in all conditions. CONCLUSIONS: The ESR properties of the VSF were accurately simulated under benchtop testing and dynamic gait conditions. These methods may be useful for predicting GRFR arising from gait with novel prostheses. Such data are useful to optimize prosthesis design parameters on a user-specific basis.

scholarly journals A Reduced-Order Computational Model of a Semi-Active Variable-Stiffness Foot Prosthesis

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
Michael A. McGeehan ◽  
Peter G. Adamczyk ◽  
Kieran M. Nichols ◽  
Michael E. Hahn
Keyword(s):  
Body Weight ◽  
Mean Squared Error ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Variable Stiffness ◽  
Performance Standard ◽  
Design Parameters ◽  
Compression Tests ◽  
Static Compression ◽  
Lumped Parameter

Abstract Passive energy storage and return (ESR) feet are current performance standard in lower limb prostheses. A recently developed semi-active variable-stiffness foot (VSF) prosthesis balances the simplicity of a passive ESR device with the adaptability of a powered design. The purpose of this study was to model and simulate the ESR properties of the VSF prosthesis. The ESR properties of the VSF were modeled as a lumped parameter overhung beam. The overhung length is variable, allowing the model to exhibit variable ESR stiffness. Foot-ground contact was modeled using sphere-to-plane contact models. Contact parameters were optimized to represent the geometry and dynamics of the VSF and its foam base. Static compression tests and gait were simulated. Simulation outcomes were compared to corresponding experimental data. Stiffness of the model matched that of the physical VSF (R2: 0.98, root-mean-squared error (RMSE): 1.37 N/mm). Model-predicted resultant ground reaction force (GRFR) matched well under optimized parameter conditions (R2: 0.98, RMSE: 5.3% body weight,) and unoptimized parameter conditions (R2: 0.90, mean RMSE: 13% body weight). Anterior–posterior center of pressure matched well with R2 > 0.94 and RMSE < 9.5% foot length in all conditions. The ESR properties of the VSF were accurately simulated under benchtop testing and dynamic gait conditions. These methods may be useful for predicting GRFR arising from gait with novel prostheses. Such data are useful to optimize prosthesis design parameters on a user-specific basis.

scholarly journals EFFECTS OF A PROSTHETIC FOOT WITH INCREASED CORONAL ADAPTABILITY ON CROSS-SLOPE WALKING

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Björn Altenburg ◽  
Michael Ernst ◽  
Pawel Maciejasz ◽  
Thomas Schmalz ◽  
Frank Braatz ◽  
...  
Keyword(s):  
Lower Limb ◽  
Patient Reported Outcomes ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Frontal Plane ◽  
Limb Amputation ◽  
The Novel ◽  
Perceived Safety ◽  
Prosthetic Foot ◽  
Patient Reported

BACKGROUND: Walking on cross-slopes is a common but challenging task for persons with lower limb amputation. The uneven ground and the resulting functional leg length discrepancy in this situation requires adaptability of both user and prosthesis. OBJECTIVE(S): This study investigated the effects of a novel prosthetic foot that offers adaptability on cross-slope surfaces, using instrumented gait analysis and patient-reported outcomes. Moreover, the results were compared with two common prosthetic feet.  METHODOLOGY: Twelve individuals with unilateral transtibial amputation and ten able-bodied control subjects participated in this randomized cross-over study. Participants walked on level ground and ±10° inclined cross-slopes at a self-selected walking speed. There were three prosthetic foot interventions: Triton Side Flex (TSF), Triton LP and Pro-Flex LP. The accommodation time for each foot was at least 4 weeks. The main outcome measures were as follows: frontal plane adaptation of shoe and prosthetic foot keel, mediolateral course of the center of pressure, ground reaction force in vertical and mediolateral direction, external knee adduction moment, gait speed, stance phase duration, step length and step width. Patient-reported outcomes assessed were the Activities Specific Balanced Confidence (ABC) scale, Prosthetic Limb Users Survey of Mobility (PLUS M) and Activities of Daily Living Questionnaire (ADL-Q).  FINDINGS: The TSF prosthetic foot adapted both faster and to a greater extent to the cross-slope conditions compared to the Triton LP and Pro-Flex LP. The graphs for the mediolateral center of pressure course and mediolateral ground reaction force showed a distinct grouping for level ground and ±10° cross-slopes, similar to control subjects. In the ADL-Q, participants reported a higher level of perceived safety and comfort when using the TSF on cross-slopes. Eight out of twelve participants preferred the TSF over the reference. CONCLUSION: The frontal plane adaptation characteristics of the TSF prosthetic foot appear to be beneficial to the user and thus may enhance locomotion on uneven ground – specifically on cross-slopes. Layman's Abstract Walking on cross-slopes is a common but challenging task for persons with lower limb amputation. The adaptability of prostheses is limited. Users alter gait strategies to cope with uneven ground. The prosthetic foot is a central component of a lower limb prosthesis. This study investigated if a novel prosthetic foot with greater adaptability is beneficial on cross-slopes. Twelve individuals with transtibial amputation (ITTAs) took part in the study. In addition, ten abled-bodied persons were measured as controls. The ITTAs were fitted with the novel foot and a reference foot. The accommodation time for each foot was four weeks at least. Afterwards gait data and patient-reported outcomes were assessed. The analyzed gait data showed clear differences in terrain compliance for the measured feet. The novel foot adapts both faster and to a greater extent to the cross-slope conditions. The self-reported outcome measures revealed better comfort and perceived safety when using the adaptive foot concept in comparison to the commercial reference. These results suggest that the adaptation characteristics of the novel foot concept are beneficial to the user. Thus, it may enhance locomotion on uneven ground such as cross-slopes. Article PDF Link: How To Cite: Altenburg B, Ernst M, Maciejasz P, Schmalz T, Braatz F, Gerke H, Bellmann M. Effects of a prosthetic foot with increased coronal adaptability on cross-slope walking. Canadian Prosthetics & Orthotics Journal. 2021;Volume 4, Issue 1, No.7.  https://doi.org/10.33137/cpoj.v4i1.35206 Corresponding Author: Björn Altenburg,Research Biomechanics, Ottobock SE & Co. KGaA, Göttingen, Germany.E-Mail: [email protected] ID: https://orcid.org/0000-0002-3484-4346  

scholarly journals Contribution of passive actions to the lower limb joint moments and powers during gait: A comparison of models

2018 ◽  
Vol 232 (8) ◽  
pp. 768-778 ◽  
Author(s):  
Xavier Gasparutto ◽  
Eric Jacquelin ◽  
Raphael Dumas
Keyword(s):  
Lower Limb ◽  
Significant Contribution ◽  
Contact Forces ◽  
Ground Reaction Forces ◽  
Joint Moments ◽  
Passive Joint ◽  
Musculoskeletal Models ◽  
Reaction Forces ◽  
The Right ◽  
Joint Limits

The lower limb passive actions representing the actions of all the passive periarticular structures have been shown to have a significant contribution to the power generation and absorption during gait. However, the respective magnitude of its different components was not established, although models of ligament moment were implemented in some musculoskeletal models. These ligament moments have shown to have an influence on the musculo-tendon forces and contact forces but the models used were never specifically evaluated, that is, compared to the passive and net joint moments. Two models of passive joint moments and three models of ligament moments were selected from the literature. Ten subjects (23–29 years old, 79.8 ± 9.5 kg, 1.85 ± 0.06 m) participated in the study. Each subject performed three gait cycles in a gait laboratory to acquire the kinematics and ground reaction forces and to compute the ligament, passive and net moments of the right lower limb joints. The contributions of the passive joint moments to the net joint moments were in accordance with the literature, although time shifts appeared for peaks in the hip and knee powers. Two of the models of ligament moments seemed, in fact, to represent the passive joint moments as their contributions were very similar while the third model of ligament moments seemed to represent only penalty-based joint limits. As a conclusion, this study showed that the models of ligament moments existing in the literature do not seem reliable. This study also demonstrated that the use of non-subject-specific models of the passive joint moments could be a valid approach for healthy subjects.

Effect of Flow-Induced Radial Load on Brush Seal/Rotor Contact Mechanics

2004 ◽  
Vol 126 (1) ◽  
pp. 208-215 ◽  
Author(s):  
Haifang Zhao ◽  
Robert J. Stango
Keyword(s):  
Flexural Rigidity ◽  
Reaction Force ◽  
Contact Forces ◽  
Design Parameters ◽  
Radial Load ◽  
Bending Stress ◽  
Seal Design ◽  
Brush Seal ◽  
Rotor Surface ◽  
Brush Seals

Brush seals comprised of special-alloy wire bristles are currently being used in lieu of traditional labyrinth seals for turbomachinery applications. This advancement in seal technology utilizes close-packed bristles that readily undergo lateral deformation arising from aerodynamic loads as well as loads imparted by the rotor surface. Thus, during operation, filament tips remain in contact with the rotor surface, which, in turn, inhibits leakage between successive stages of the turbine, and increases engine efficiency. However, contact forces generated at the interface of the rotor and fiber tips can lead to eventual bristle fatigue and wear of the seal/rotor system. Therefore, it is important that reliable modeling techniques be developed that can help identify complex relationships among brush seal design parameters, in-service loads, and contact forces that arise during the operation of turbomachinery. This paper is concerned with modeling and evaluating bristle deformation, bending stress, and bristle/rotor contact forces that are generated at the interface of the fiber and rotor surface due to radial fluid flow, and augments previous work reported by the author’s, which assessed filament tip forces that arise solely due to interference between the bristle/rotor. The current problem derives its importance from aerodynamic forces that are termed “blow-down,” that is, the inward radial flow of gas in close proximity to the face of the seal. Thus, bristle deformation, bristle tip reaction force, and bristle bending stress is computed on the basis of an in-plane, large-displacement mechanics analysis of a cantilever beam that is subjected to a uniform radial load. Solutions to the problem are obtained for which the filament tip is constrained to lie on the rotor surface, and includes the effect of Coulombic friction at the interface of the fiber tip and rotor. Contact forces are obtained for a range of brush seal design parameters including fiber lay angle, flexural rigidity, and length. In addition, the governing equation is cast in non-dimensional form, which extends the range of applicability of solutions to brush seals having a more general geometry and material composition.

Applications of Musculoskeletal Modelling and Simulation for Lower-Limb Prosthesis Design Optimization

2018 ◽  
Author(s):  
Emerson Paul Grabke ◽  
Jan Andrysek
Keyword(s):  
Design Optimization ◽  
Lower Limb ◽  
Predictive Modelling ◽  
Musculoskeletal Model ◽  
Modelling And Simulation ◽  
Prosthesis Design ◽  
Model Complexity ◽  
Patient Specific ◽  
Musculoskeletal Modelling ◽  
Musculoskeletal Models

Lower-limb amputees can suffer from preventable pain and bone disorders attributable to suboptimal prosthesis design. Predictive modelling and simulation of human walking using conventional biomechanical gait models offer an alternative to intuition-based prosthesis design, providing insight into the biomechanics underlying pathological gait. Musculoskeletal models additionally enable understanding of prosthesis contributions to the human musculoskeletal system, and both prosthesis and individual muscle contributions to body support and propulsion during gait. Based on this review, forward dynamic simulation of amputee musculoskeletal models have been used to perform prosthesis design optimization using optimal control and reflex-based control. Musculoskeletal model complexity and assumptions inhibit fully predictive musculoskeletal modelling in its current state, hindering computational prosthesis design optimization. Future recommendations include validating musculoskeletal models and resultant optimized prosthesis designs, developing less computationally-expensive predictive musculoskeletal modelling methods, and developing more efficient patient-specific musculoskeletal model generation methods to enable personalized prosthesis optimization.

A Hub Dynamometer for Measurement of Wheel Forces in Off-Road Bicycling

1999 ◽  
Vol 121 (1) ◽  
pp. 132-137 ◽  
Author(s):  
D. S. De Lorenzo ◽  
M. L. Hull
Keyword(s):  
Measurement Errors ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Front Wheel ◽  
Full Scale ◽  
Contact Forces ◽  
Ground Contact ◽  
Strain Gages ◽  
Accuracy Check ◽  
Force Components

A dynamometric hubset that measures the two ground contact force components acting on a bicycle wheel in the plane of the bicycle during off-road riding while either coasting or braking was designed, constructed, and evaluated. To maintain compatibility with standard mountain bike construction, the hubs use commercially available shells with modified, strain gage-equipped axles. The axle strain gages are sensitive to forces acting in the radial and tangential directions, while minimizing sensitivity to transverse forces, steering moments, and variations in the lateral location of the center of pressure. Static calibration and a subsequent accuracy check that computed differences between applied and apparent loads developed during coasting revealed root mean squared errors of 1 percent full-scale or less (full-scale load = 4500 N). The natural frequency of the rear hub with the wheel attached exceeded 350 Hz. These performance capabilities make the dynamometer useful for its intended purpose during coasting. To demonstrate this usefulness, sample ground contact forces are presented for a subject who coasted downhill over rough terrain. The dynamometric hubset can also be used to determine ground contact forces during braking providing that the brake reaction force components are known. However, compliance of the fork can lead to high cross-sensitivity and corresponding large (>5 percent FS) measurement errors at the front wheel.

Biomechanical Performance of Habitually Barefoot and Shod Runners during Barefoot Jogging and Running

2018 ◽  
Vol 38 ◽  
pp. 1-10 ◽  
Author(s):  
Suo Di Xu ◽  
Zhi Qiang Liang ◽  
Yu Wei Liu ◽  
Gusztáv Fekete
Keyword(s):  
Lower Limb ◽  
Sagittal Plane ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Three Dimensional ◽  
Frontal Plane ◽  
Influential Factor ◽  
Hip Abduction ◽  
Foot Strike ◽  
Limb Kinematics

The purpose of this study was to evaluate the biomechanical performances, running stability of habitually barefoot (BR) and shod runners (SR) during barefoot jogging and running. Ten healthy male subjects, 5 habitually shod runners and 5 habitually barefoot runners, from two different ethnics participated in this study. Subjects performed jogging (2m/s) and running (4m/s) along a 10-m runway. Three-dimensional lower-limb kinematics, ground reaction force, center of pressure (COP) and contact time (CT), were collected during testing. During jogging and running, all participants adopted rear-foot strike pattern, SR had larger VALR. SR showed significantly larger lower-limb range of motion (ROM) in sagittal plane, significantly larger hip abduction and opposite knee ROM in frontal plane, as well as significantly larger ankle internal rotation in horizontal plane. All participants’ CT showed decreased trend with running speed up; and SR was significantly longer than BR; BR and SR in COP showed different trajectories, especially forefoot and rearfoot areas. Habitually barefoot and shod runner from different ethnics still exist significant differences in lower-extremity ROM; and different foot morphological of participants is an important influential factor for these variations.

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