Instantaneous stiffness and hysteresis of dynamic elastic response prosthetic feet

2016 ◽  
Vol 41 (5) ◽  
pp. 463-468 ◽  
Author(s):  
Christina M Webber ◽  
Kenton Kaufman
Keyword(s):  
Carbon Fiber ◽  
Mechanical Testing ◽  
Elastic Response ◽  
Glass Composite ◽  
Prosthetic Foot ◽  
Proof Testing ◽  
Objective Evidence ◽  
Objective Performance ◽  
Reproducible Method ◽  
Prosthetic Feet

Background:Dynamic elastic response prosthetic feet are designed to mimic the functional characteristics of the native foot/ankle joint. Numerous designs of dynamic elastic response feet exist which make the prescription process difficult, especially because of the lack of empirical evidence describing the objective performance characteristics of the feet.Objectives:To quantify the mechanical properties of available dynamic elastic response prosthetic feet, specifically the stiffness and hysteresis.Study design:Mechanical testing of dynamic elastic response prosthetic feet.Methods:Static Proof Testing in accordance with ISO 10328 was conducted on seven dynamic elastic response prosthetic feet. Load–displacement data were used to calculate the instantaneous stiffness in both the heel and forefoot regions, as well as hysteresis associated with each foot.Results:Heel stiffness was greater than forefoot stiffness for all feet. The heel of the glass composite prosthetic foot was stiffer than the carbon fiber feet and it exhibited less hysteresis. Two different carbon fiber feet had the stiffest forefoot regions.Conclusion:Mechanical testing is a reproducible method that can be used to provide objective evidence about dynamic elastic response prosthetic foot performance and aid in the prescription process.Clinical relevanceThe quantitative stiffness and hysteresis data from this study can be used by prosthetists to aid the prescription process and make it more objective.

Significance of Nonsagittal Power Terms in Analysis of a Dynamic Elastic Response Prosthetic Foot

1999 ◽  
Vol 121 (5) ◽  
pp. 521-524 ◽  
Author(s):  
M. D. Geil ◽  
M. Parnianpour ◽  
N. Berme
Keyword(s):  
Ankle Joint ◽  
High Performance ◽  
Sagittal Plane ◽  
Transverse Plane ◽  
Elastic Response ◽  
Joint Power ◽  
Prosthetic Foot ◽  
Prosthetic Feet ◽  
Carbon Copy

Dynamic elastic response prosthetic feet generally utilize a solid ankle, limiting dominant motion to the sagittal plane. However, researchers often use total rotational ankle joint power in the analysis of these feet. This investigation measured joint power terms in each plane for the Carbon Copy High Performance prosthetic foot. The significance of the frontal and transverse plane terms was assessed. Addition of these terms to the dominant sagittal power term revealed only slight differences, indicating that the sagittal power term is likely sufficient.

Roll-over analysis of a new design carbon fiber prosthetic foot

2019 ◽  
Author(s):  
Mohsin Noori Hamzah ◽  
Abdurrahman AbdulhessenGatta
Keyword(s):  
Carbon Fiber ◽  
Prosthetic Foot

Characterizing adaptations of prosthetic feet in the frontal plane

2020 ◽  
Vol 44 (4) ◽  
pp. 225-233
Author(s):  
Michael Ernst ◽  
Björn Altenburg ◽  
Thomas Schmalz
Keyword(s):  
Energy Storage ◽  
Theoretical Model ◽  
Ankle Joint ◽  
Frontal Plane ◽  
Measured Data ◽  
Limb Amputation ◽  
Clinical Parameters ◽  
Mechanical Adaptation ◽  
Prosthetic Foot ◽  
Prosthetic Feet

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.

Parametric Evaluation of Hindfoot and Forefoot Properties and Their Effect on the Angular Stiffness of Prosthetic Feet

2012 ◽  
Author(s):  
Peter G. Adamczyk ◽  
Michelle Roland ◽  
Michael E. Hahn
Keyword(s):  
Stance Phase ◽  
Direct Calculation ◽  
Future Studies ◽  
Prosthetic Foot ◽  
Moment Arms ◽  
Walking Performance ◽  
Deformation Mechanics ◽  
Prosthetic Feet ◽  
Stiffness Characteristics ◽  
Parametric Adjustment

Prosthetic foot stiffness has been recognized as an important factor in optimizing the walking performance of amputees [1–3]. Commercial feet are available in a range of stiffness categories and geometries. The stiffness of linear displacements of the hindfoot and forefoot for several commercially available feet have been reported to be within a range of 27–68 N/mm [4] and 28–76 N/mm [5], respectively, but these values are most relevant only to the earliest and latest portions of stance phase, when linear compression or rebound naturally occur. In contrast, mid-stance kinetics are more related to the angular stiffness of the foot, which describes the ankle torque produced by angular progression of the lower limb over the foot during this phase. Little data is available regarding the angular stiffness of any commercially available feet. The variety of geometries between manufacturers and models of prosthetic feet makes a direct calculation of effective angular stiffness challenging due to changes in moment arms based on loading condition, intricacies of deformation mechanics of the structural components, and mechanical interaction between hindfoot and forefoot components. Thus, modeling the interaction between hindfoot stiffness, forefoot stiffness, and keel geometries and their combined effect on the angular stiffness of the foot may be a useful tool for correlating functional outcomes with stiffness characteristics of various feet. To understand how each of these factors affects angular stiffness, we developed a foot that can parametrically adjust each of these factors independently. The objective of this study was to mathematically model, design, and experimentally validate a prosthetic foot that has independent hindfoot and forefoot components, allowing for parametric adjustment of stiffness characteristics and keel geometry in future studies of amputee gait.

Influence of gait training and prosthetic foot category on external work symmetry during unilateral transtibial amputee gait

2013 ◽  
Vol 37 (5) ◽  
pp. 396-403 ◽  
Author(s):  
Vibhor Agrawal ◽  
Robert Gailey ◽  
Christopher O’Toole ◽  
Ignacio Gaunaurd ◽  
Adam Finnieston
Keyword(s):  
Repeated Measures ◽  
Gait Training ◽  
Third Party ◽  
External Work ◽  
Gait Dynamics ◽  
Prosthetic Foot ◽  
Negative Work ◽  
Level 3 ◽  
Prosthetic Feet ◽  
Level 2

Background:Prosthetic foot prescription guidelines lack scientific evidence and are concurrent with an amputee’s concurrent with an amputee’s Medicare Functional Classification Level (K-Level) and categorization of prosthetic feet.Objective:To evaluate the influence of gait training and four categories of prosthetic feet (K1, K2, K3, and microprocessor ankle/foot) on Symmetry in External Work for K-Level-2 and K-Level-3 unilateral transtibial amputees.Design:Randomized repeated-measures trial.Methods:Five K-Level-2 and five K-Level-3 subjects were tested in their existing prosthesis during Session 1 and again in Session 2, following 2 weeks of standardized gait training. In Sessions 3–6, subjects were tested using a study socket and one of four randomized test feet. There was an accommodation period of 10–14 days with each foot. Symmetry in External Work for positive and negative work was calculated at each session to determine symmetry of gait dynamics between limbs at self-selected walking speeds.Results:K-Level-2 subjects had significantly higher negative work symmetry with the K3 foot, compared to K1/K2 feet. For both subject groups, gait training had a greater impact on positive work symmetry than test feet.Conclusion:Higher work symmetry is possible for K-Level-2 amputees who are trained to take advantage of K3 prosthetic feet designs. There exists a need for an objective determinant for categorizing and prescribing prosthetic feet.Clinical relevanceFindings that gait training can influence symmetry of gait dynamics and that K-Level-2 amputees can achieve greater work symmetry with a K3 foot having a “J-shaped” ankle and heel-to-toe footplate could potentially impact prosthetic care and foot prescription by clinicians and reimbursement guidelines by third-party health-care payers.

Biomechanical Model Representing Energy Storing Prosthetic Feet

2010 ◽  
Author(s):  
Francy L. Sinatra ◽  
Stephanie L. Carey ◽  
Rajiv Dubey
Keyword(s):  
Motion Analysis ◽  
Lower Limb ◽  
Biomechanical Model ◽  
Body Segment ◽  
Prosthetic Foot ◽  
Biomechanical Models ◽  
Prosthetic Feet ◽  
Analysis System ◽  
Lower Limb Amputees ◽  
Metabolic Information

Previous studies have been conducted to develop a biomechanical model for a human’s lower limb. Amongst them, there have been several studies trying to quantify the kinetics and kinematics of lower-limb amputees through motion analysis [5, 10, 11]. Currently, there are various designs for lower-limb prosthetic feet such as the Solid Ankle Cushion Heel (SACH) from Otto Bock (Minneapolis) or the Flex Foot from Ossur (California). The latter is a prosthetic foot that allows for flexibility while walking and running. Special interest has been placed in recording the capabilities of these energy-storing prosthetic feet. This has been done through the creation of biomechanical models with motion analysis. In these previous studies the foot has been modeled as a single rigid-body segment, creating difficulties when trying to calculate the power dissipated by the foot [5, 20, 21]. This project studies prosthetic feet with energy-storing capabilities. The purpose is to develop an effective way of calculating power by using a biomechanical model. This was accomplished by collecting biomechanical data using an eight camera VICON (Colorado) motion analysis system including two AMTI (BP-400600, Massachusetts) force plates. The marker set that was used, models the foot using several segments, hence mimicking the motion the foot undergoes and potentially leading to greater accuracy. By developing this new marker set, it will be possible to combine the kinematic and kinetic profile gathered from it with previous studies that determined metabolic information. This information will allow for the better quantification and comparison of the energy storage and return (ES AR) feet and perhaps the development of new designs.

Effect of Walking Speed on Angular Stiffness and Roll-Over Shape of the Intact and Prosthetic Feet of Transtibial Amputees

2013 ◽  
Author(s):  
Michelle Roland ◽  
Peter G. Adamczyk ◽  
Michael E. Hahn
Keyword(s):  
Lower Limb ◽  
Stance Phase ◽  
Walking Speed ◽  
Plantar Flexor ◽  
Limb Function ◽  
Prosthetic Foot ◽  
Material Stiffness ◽  
Prosthetic Feet ◽  
Transtibial Amputees ◽  
Lower Limb Function

The calculated roll-over shape and respective radius of intact and prosthetic feet has been shown to be a useful measure of lower limb function during walking [1–2]. Hansen et al [3] reported that the roll-over radius, R, is constant over a range of speeds for the intact foot-ankle system. It may be assumed that the prosthetic foot R would also be constant with increased walking speed. Similarly, the angular stiffness of prosthetic feet is not likely to change with walking speed, as the material stiffness remains unchanged. However, the effective angular stiffness of the intact ankle may increase with the plantar flexor moment during the stance phase of gait, which typically increases in magnitude with walking speed.

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