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.

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  

Multi-Keel Passive Prosthetic Foot Design Optimization Using the Lower Leg Trajectory Error Framework

2021 ◽  
Author(s):  
Victor Prost ◽  
Heidi V. Peterson ◽  
Amos G. Winter
Keyword(s):  
Low Cost ◽  
Lower Leg ◽  
International Standards ◽  
Limb Amputation ◽  
Average Error ◽  
Static Tests ◽  
Prosthetic Devices ◽  
Trajectory Error ◽  
Prosthetic Foot ◽  
Prosthetic Feet

Abstract People with lower-limb amputation in low- and middle-income countries (LMICs) lack access to adequate prosthetic devices that would restore their mobility and increase their quality of life. This is largely due to the cost and durability of existing devices. Single-keel energy storage and return (ESR) prosthetic feet have recently been developed to provide improved walking benefits at an affordable cost in LMICs. These low-cost single-keel ESR feet were created using a novel design methodology, the lower leg trajectory error (LLTE) framework. The LLTE framework enables the optimization of the stiffness and geometry of a user’s prosthesis to match a target walking pattern. However, these low-cost single-keel ESR prostheses do not provide the required durability to fulfill the international standards organization (ISO) testing, which prevents their widespread use and adoption. In this work, we developed a multi-keel prosthetic foot parametric model, and extended the LLTE framework to include this multi-keel architecture and the durability requirements. This extended LLTE framework enabled the design of durable and low-cost multi-keel ESR prosthetic feet made of Nylon 6/6. Multi-keel foot designs were shown to provide 76% improved walking performance (lower LLTE values) compared with single-keel ESR designs. Load testing of prototype multi-keel feet validated the multi-keel constitutive model predictions used in the LLTE framework. The measured deflections of the prototypes under load were accurately described with an average error of 0.6 ± 0.4 mm (5.7 ± 4.2%). These multi-keel feet designed using the extended LLTE framework withstood ISO fatigue and static tests, validating their durability. Given their single-part 2D extruded geometries, multi-keel feet designed with the extended LLTE framework could be cost-effectively manufactured, providing affordable and durable high-performance prostheses that improves the mobility of LMIC users.

scholarly journals Design and Testing of a Prosthetic Foot With Interchangeable Custom Springs for Evaluating Lower Leg Trajectory Error, an Optimization Metric for Prosthetic Feet

2018 ◽  
Vol 10 (2) ◽  
Author(s):  
Victor Prost ◽  
Kathryn M. Olesnavage ◽  
W. Brett Johnson ◽  
Matthew J. Major ◽  
Amos G. Winter
Keyword(s):  
Range Of Motion ◽  
Ankle Joint ◽  
Large Scale ◽  
Joint Stiffness ◽  
Lower Leg ◽  
Trajectory Error ◽  
Prosthetic Foot ◽  
Design Variables ◽  
Prosthetic Feet

An experimental prosthetic foot intended for evaluating a novel design objective is presented. This objective, called the lower leg trajectory error (LLTE), enables the optimization of passive prosthetic feet by modeling the trajectory of the shank during single support for a given prosthetic foot and selecting design variables that minimize the error between this trajectory and able-bodied kinematics. A light-weight, fully characterized test foot with variable ankle joint stiffness was designed to evaluate the LLTE. The test foot can replicate the range of motion of a physiological ankle over a range of different ankle joint stiffnesses. The test foot consists of a rotational ankle joint machined from acetal resin, interchangeable U-shaped nylon springs that range from 1.5 N · m/deg to 24 N · m/deg, and a flexible nylon forefoot with a bending stiffness of 16 N · m2. The U-shaped springs were designed to support a constant moment along their length to maximize strain energy density; this feature was critical in creating a high-stiffness and high-range of motion ankle. The design performed as predicted during mechanical and in vivo testing, and its modularity allowed us to rapidly vary the ankle joint stiffness. Qualitative feedback from preliminary testing showed that this design is ready for use in large scale clinical trials to further evaluate the use of the LLTE as an optimization objective for passive prosthetic feet.

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

2019 ◽  
Vol 43 (3) ◽  
pp. 266-275 ◽  
Author(s):  
Nicholas D Womac ◽  
Richard R Neptune ◽  
Glenn K Klute
Keyword(s):  
Mechanical Properties ◽  
Energy Storage ◽  
Graphical User Interface ◽  
Lateral Loading ◽  
Prosthetic Foot ◽  
Limb Loading ◽  
Prosthetic Feet ◽  
Force Displacement ◽  
Storage Characteristics ◽  
Graphical User Interface Tool

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.

The Effect of High- and Low-Damping Prosthetic Foot Structures on Knee Loading in the Uninvolved Limb Across Different Walking Speeds

2016 ◽  
Vol 32 (3) ◽  
pp. 233-240 ◽  
Author(s):  
Li Jin ◽  
Peter G. Adamczyk ◽  
Michelle Roland ◽  
Michael E. Hahn
Keyword(s):  
Knee Osteoarthritis ◽  
Frontal Plane ◽  
Limb Amputation ◽  
Loading Rates ◽  
Prosthetic Foot ◽  
Fast Speed ◽  
Peak Knee ◽  
Knee Loading ◽  
Young Subjects ◽  
Walking Speeds

Lower limb amputation has been associated with secondary impairments such as knee osteoarthritis in the uninvolved limb. Greater knee loading in the frontal plane has been related to severity and rate of progression in knee osteoarthritis. Reduced push-off work from the involved limb can increase uninvolved limb knee loading. However, little is known about specific effects that prosthetic foot damping may have on uninvolved limb loading. We hypothesized that uninvolved limb peak knee internal abduction moment (IAM) and loading rates would be greater when using a high-damping foot compared with a low-damping foot, across walking speeds. Eight healthy, young subjects walked in a prosthesis simulator boot using the experimental feet. Greater uninvolved limb first peak IAM (+16% in fast speed, P = .002; +11% in slow speed, P = .001) and loading rates (+11% in fast speed, P = .003) were observed when using the high-damping foot compared with low-damping foot. Within each foot, uninvolved limb first peak IAM and loading rates had a trend to increase with increased walking speed. These findings suggest that damping properties of prosthetic feet are related to uninvolved limb peak knee IAM and loading rates.

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.

scholarly journals Analysis of Rollover Shape and Energy Storage and Return in Cantilever Beam-Type Prosthetic Feet

2014 ◽  
Author(s):  
Kathryn M. Olesnavage ◽  
Amos G. Winter
Keyword(s):  
Energy Storage ◽  
Cantilever Beam ◽  
Cross Section ◽  
Stance Phase ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Heel Strike ◽  
Prosthetic Foot ◽  
Beam Type ◽  
Prosthetic Feet

This paper presents an analysis of the rollover shape and energy storage and return in a prosthetic foot made from a compliant cantilevered beam. The rollover shape of a prosthetic foot is defined as the path of the center of pressure along the bottom of the foot during stance phase of gait, from heel strike to toe off. This path is rotated into the reference frame of the ankle-knee segment of the leg, which is held fixed. In order to achieve correct limb loading and gait kinematics, it is important that a prosthetic foot both mimic the physiological rollover shape and maximize energy storage and return. The majority of prosthetic feet available on the market are cantilever beam-type feet that emulate ankle dorsiflexion through beam bending. In this study, we show analytically that a prosthetic foot consisting of a beam with constant or monotonically decreasing cross-section cannot replicate physiological rollover shape; the foot is either too stiff when the ground reaction force (GRF) acts near the ankle, or too compliant when the GRF acts near the toe. A rigid constraint is required to prevent the foot from over-deflecting. Using finite element analysis (FEA), we investigated how closely a cantilever beam with constrained maximum deflection could mimic physiological rollover shape and energy storage/return during stance phase. A constrained beam with constant cross-section is able to replicate physiological rollover shape with R2 = 0.86. The ratio of the strain energy stored and returned by the beam compared to the ideal energy storage and return is 0.504. This paper determines that there is a trade off between rollover shape and energy storage and return in cantilever beam-type prosthetic feet. The method and results presented in this paper demonstrate a useful tool in early stage prosthetic foot design that can be used to predict the rollover shape and energy storage of any type of prosthetic foot.

scholarly journals Measurement of passive ankle stiffness in subjects with chronic hemiparesis using a novel ankle robot

2011 ◽  
Vol 105 (5) ◽  
pp. 2132-2149 ◽  
Author(s):  
Anindo Roy ◽  
Hermano I. Krebs ◽  
Christopher T. Bever ◽  
Larry W. Forrester ◽  
Richard F. Macko ◽  
...  
Keyword(s):  
Ankle Joint ◽  
Frontal Plane ◽  
Chronic Stroke ◽  
Healthy Adults ◽  
Stroke Survivors ◽  
Passive Stiffness ◽  
Mechanical Stiffness ◽  
Treatment Protocols ◽  
Ankle Stiffness ◽  
Hemiparetic Stroke

Our objective in this study was to assess passive mechanical stiffness in the ankle of chronic hemiparetic stroke survivors and to compare it with those of healthy young and older (age-matched) individuals. Given the importance of the ankle during locomotion, an accurate estimate of passive ankle stiffness would be valuable for locomotor rehabilitation, potentially providing a measure of recovery and a quantitative basis to design treatment protocols. Using a novel ankle robot, we characterized passive ankle stiffness both in sagittal and in frontal planes by applying perturbations to the ankle joint over the entire range of motion with subjects in a relaxed state. We found that passive stiffness of the affected ankle joint was significantly higher in chronic stroke survivors than in healthy adults of a similar cohort, both in the sagittal as well as frontal plane of movement, in three out of four directions tested with indistinguishable stiffness values in plantarflexion direction. Our findings are comparable to the literature, thus indicating its plausibility, and, to our knowledge, report for the first time passive stiffness in the frontal plane for persons with chronic stroke and older healthy adults.

scholarly journals An Effective Measured Data Preprocessing Method in Electrical Impedance Tomography

2014 ◽  
Vol 2014 ◽  
pp. 1-15 ◽  
Author(s):  
Chenglong Yu ◽  
Shihong Yue ◽  
Jianpei Wang ◽  
Huaxiang Wang
Keyword(s):  
Theoretical Model ◽  
Electrical Impedance Tomography ◽  
Electrical Impedance ◽  
Data Preprocessing ◽  
Measured Data ◽  
General Criterion ◽  
Impedance Tomography ◽  
Preprocessing Method ◽  
Detection Technology ◽  
Process Detection

As an advanced process detection technology, electrical impedance tomography (EIT) has widely been paid attention to and studied in the industrial fields. But the EIT techniques are greatly limited to the low spatial resolutions. This problem may result from the incorrect preprocessing of measuring data and lack of general criterion to evaluate different preprocessing processes. In this paper, an EIT data preprocessing method is proposed by all rooting measured data and evaluated by two constructed indexes based on all rooted EIT measured data. By finding the optimums of the two indexes, the proposed method can be applied to improve the EIT imaging spatial resolutions. In terms of a theoretical model, the optimal rooting times of the two indexes range in [0.23, 0.33] and in [0.22, 0.35], respectively. Moreover, these factors that affect the correctness of the proposed method are generally analyzed. The measuring data preprocessing is necessary and helpful for any imaging process. Thus, the proposed method can be generally and widely used in any imaging process. Experimental results validate the two proposed indexes.

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