Biomechanical characteristics, patient preference and activity level with different prosthetic feet: a randomized double blind trial with laboratory and community testing

Variable-stiffness prosthesis improves biomechanics of walking across speeds compared to a passive device

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.

The development of rating scales to evaluate experiential prosthetic foot preference for people with lower limb amputation

BACKGROUND

Selection of a foot is an important aspect of prosthetic prescription and vital to maximizing mobility and functional goals after lower limb amputation. Development of a standardized approach to soliciting user experiential preferences is needed to improve evaluation and comparison of prosthetic feet.

OBJECTIVE

To develop rating scales to assess prosthetic foot preference and to evaluate use of these scales in people with transtibial amputation after trialing different prosthetic feet.

DESIGN

Participant-blinded, repeated measures crossover trial.

SETTING

Veterans Affairs and Department of Defense Medical Centers, laboratory setting.

PARTICIPANTS

Seventy-two male prosthesis users with unilateral transtibial amputation started, and 68 participants completed this study.

INTERVENTIONS

Participants trialed three mobility-level appropriate commercial prosthetic feet briefly in the laboratory.

MAIN OUTCOME MEASURES

"Activity-specific" rating scales were developed to assess participants' ability with a given prosthetic foot to perform typical mobility activities (eg, walking at different speeds, on inclines, and stairs) and "global" scales to rate overall perceived energy required to walk, satisfaction, and willingness to regularly use the prosthetic foot. Foot preference was determined by comparing the rating scale scores, after laboratory testing.

RESULTS

The greatest within-participant differences in scores among feet were observed in the "incline" activity, where 57% ± 6% of participants reported 2+ point differences. There was a significant association (p < .05) between all "activity-specific" rating scores (except standing) and each "global" rating score.

CONCLUSIONS

The standardized rating scales developed in this study could be used to assess prosthetic foot preference in both the research and clinical settings to guide prosthetic foot prescription for people with lower limb amputation capable of a range of mobility levels.

The Moment Criterion of Anthropomorphicity of Prosthetic Feet as a Potential Predictor of Their Functionality for Transtibial Amputees

The purpose of this paper is to discuss a new quantitative mechanical parameter of prosthetic feet called the Index of Anthropomorphicity (IA), which has the potential to be adopted as an objective predictor of their functionality. The objectives are to present the research findings supporting the introduction of IA and unify previous results into a coherent theory. The IA is founded on the moment criterion of the anthropomorphicity of prosthetic feet. The term "anthropomorphicity" is defined for this application. Studies with a small number of human subjects and prostheses have shown that the value of the parameter is positively correlated with patient comfort and with the restoration of certain normal gait characteristics. Confirmatory studies with controlled human trials and mechanical tests with a wider selection of prosthesis types can give prosthesis manufacturers a new criterion to follow in the design process, and prosthetists may use the IA for selecting more suitable prostheses for a patient's comfort and health.

A Scientometric Analysis and Visualization of Prosthetic Foot Research Work: 2000 to 2022

This study aims to highlight recent research work on topics around prosthetic feet through a scientometric analysis and historical review. The most cited publications from the Clarivate Analytics Web of Science Core Collection database were identified and analyzed from 1 January 2000 to 31 October 2022. Original articles, reviews with full manuscripts, conference proceedings, early access documents, and meeting abstracts were included. A scientometric visualization analysis of the bibliometric information related to the publications, including the countries, institutions, journals, references, and keywords, was conducted. A total of 1827 publications met the search criteria in this study. The related publications grouped by year show an overall trend of increase during the two decades from 2000 to 2022. The United States is ranked first in terms of overall influence in this field (n = 774). The Northwestern University has published the most papers on prosthetic feet (n = 84). Prosthetics and Orthotics International has published the largest number of studies on prosthetic feet (n = 151). During recent years, a number of studies with citation bursts and burst keywords (e.g., diabetes, gait, pain, and sensor) have provided clues on the hotspots of prosthetic feet and prosthetic foot trends. The findings of this study are based on a comprehensive analysis of the literature and highlight the research topics on prosthetic feet that have been primarily explored. The data provide guidance to clinicians and researchers to further studies in this field.

Low-cost prosthetic feet for underserved populations: A comparison of gait analysis and mechanical stiffness

BACKGROUND

Lower-limb loss is an ongoing cause of disability throughout the world. Despite advancements in prosthetic technologies, there are numerous underserved populations in need of effective low-cost prosthetic foot options.

OBJECTIVE

To evaluate the biomechanical performance of several low-cost prosthetic feet, using a combination of instrumented gait analysis and mechanical stiffness testing.

STUDY DESIGN

Randomized crossover with additional case study.

METHODS

We compared the solid-ankle-cushioned-heel (SACH), Jaipur, and Niagara feet with carbon fiber feet. Mechanical stiffness was evaluated using a cantilever-style bending test at 2 angles that was designed to mimic late stance gait loading. Eight below-knee amputees participated in the gait analysis, which focused on foot and ankle motion and energetics.

RESULTS

Metric analysis showed significant differences among feet in ankle motion and power as well as distal-to-shank power, with SACH showing reduced ankle motion and positive work compared with the other feet. Waveform analysis additionally revealed a compensatory knee flexion moment in SACH and a knee extension moment in Niagara and Jaipur during midstance. In mechanical stiffness testing, SACH had the highest stiffness, with Niagara and carbon fiber roughly similar, and Jaipur the most compliant with the greatest hysteresis.

CONCLUSIONS

There may be an optimal stiffness range for future prosthesis designs that maximizes propulsive energy. This may be achieved by combining some characteristics of Jaipur and Niagara feet in new designs. Ultimately, optimizing stiffness and energetics for gait biomimicry while maintaining cost, availability, and versatility across cultures will alleviate the effects of limb loss among underserved populations.

Use of machine learning in the field of prosthetics and orthotics: A systematic narrative review

Although machine learning is not yet being used in clinical practice within the fields of prosthetics and orthotics, several studies on the use of prosthetics and orthotics have been conducted. We intend to provide relevant knowledge by conducting a systematic review of prior studies on using machine learning in the fields of prosthetics and orthotics. We searched the Medical Literature Analysis and Retrieval System Online (MEDLINE), Cochrane, Embase, and Scopus databases and retrieved studies published until July 18, 2021. The study included the application of machine learning algorithms to upper-limb and lower-limb prostheses and orthoses. The criteria of the Quality in Prognosis Studies tool were used to assess the methodological quality of the studies. A total of 13 studies were included in this systematic review. In the realm of prostheses, machine learning has been used to identify prosthesis, select an appropriate prosthesis, train after wearing the prosthesis, detect falls, and manage the temperature in the socket. In the field of orthotics, machine learning was used to control real-time movement while wearing an orthosis and predict the need for an orthosis. The studies included in this systematic review are limited to the algorithm development stage. However, if the developed algorithms are actually applied to clinical practice, it is expected that it will be useful for medical staff and users to handle prosthesis and orthosis.

Sensitivity of lower-limb joint mechanics to prosthetic forefoot stiffness with a variable stiffness foot in level-ground walking

This paper presents the effectsof the Variable Stiffness Foot (VSF) on lower-limb joint mechanics in level-ground walking. Persons with transtibial amputations use lower-limb prostheses to restore level-ground walking, and foot stiffness and geometry have been shown to be the main factors for evaluating foot prostheses. Previous studies have validated the semi-active and stiffness modulation capabilities of the VSF. The core aim of this study is to investigate the mechanical effects of adjusting stiffness on knee and ankle mechanics for prosthetic users wearing the VSF. For this study, seven human participants walked with three different stiffnesses (compliant, medium, stiff) of the VSF across two force plates in a motion capture lab. Linear mixed models were utilized to estimate the significance and coefficients of determinations for the regression of stiffness on several biomechanical metrics. A stiffer VSF led to decreased ankle dorsiflexion angle (p < 0.0001, r2 = 0.90), increased ankle plantarflexor moment (p = 0.016, r2 = 0.40), increased knee extension (p = 0.021, r2 = 0.37), increased knee flexor moment (p = 0.0007, r2 = 0.63), and decreased magnitudes of prosthetic energy storage (p < 0.0001, r2 = 0.90), energy return (p = 0.0003, r2 = 0.67), and power (p < 0.0001, r2 = 0.74). These results imply lower ankle, knee, and hip moments, and more ankle angle range of motion using a less stiff VSF, which may be advantageous to persons walking with lower-limb prostheses. Responsive modulation of the VSF stiffness, according to these findings, could help overcome gait deviations associated with different slopes, terrain characteristics, or footwear.

Metatarsophalangeal Joint Dynamic Stiffness During Toe Rocker Changes With Walking Speed

Dynamic joint stiffness (or simply "stiffness") is a customization criteria used to tune mechanical properties of orthotic and prosthetic devices. This study examines metatarsophalangeal (MTP) joint stiffness during the toe-rocker phase of barefoot walking and establishes baseline characteristics of MTP joint stiffness. Ten healthy individuals walked at 4 speeds (0.4, 0.6, 0.8, and 1.0 statures·s-1) over level ground. MTP sagittal plane joint angles and moments were calculated during the toe-rocker phase of stance. Least-squares linear regressions were conducted on the MTP moment versus angle curve to determine joint stiffness during early toe rocker and late toe rocker. Multilevel linear models were used to test for statistically significant differences between conditions. Early toe rocker stiffness was positive, while late toe rocker was negative. Both early toe rocker and late toe rocker stiffness increased in magnitude significantly with speed. This study establishes baseline characteristics of MTP joint stiffness in healthy walking, which previously had not been examined through a range of controlled walking speeds. This information can be used in the future as design criteria for orthotic and prosthetic ankle and ankle-foot devices that can imitate, support, and facilitate natural human foot motion during walking better than existing devices.

Comparing forefoot and heel stiffnesses across commercial prosthetic feet manufactured for individuals with varying body weights and foot sizes

BACKGROUND

Despite the effects of prosthetic foot mechanical properties on gait of people with lower limb amputation, scant forefoot and heel stiffness data exist to help guide prosthetic foot prescription.

OBJECTIVE

To measure forefoot and heel linear stiffness properties across commonly prescribed commercial prosthetic foot models and to describe variations in stiffness across feet targeted for users with different body weights and foot sizes.

STUDY DESIGN

Mechanical testing of five types of commercial prosthetic feet across nine user body weight and foot size combinations.

METHODS

Linear forefoot and heel stiffness (force vs. displacement) data were collected for 41 prosthetic feet. Quasistatic testing was conducted at -15 and +20 degrees to isolate loading of the heel and forefoot, respectively.

RESULTS

Overall, there was a significant relationship between user body weight and both forefoot and heel stiffness, when adjusted for foot size and type ( P < 0.001). However, there were a substantial number of inconsistencies across foot type within example user body weight and foot sizes combination. Furthermore, the relative order of forefoot stiffness across foot type differed from the relative order of heel stiffness across foot type.

CONCLUSIONS

The inconsistencies and differences in relative order of forefoot and heel stiffness across commercial foot type suggest the importance of publishing objective stiffness and other mechanical properties of prosthetic feet. These data can aid clinicians in better matching mechanical properties of prosthetic feet with the functional goals and abilities of prosthesis users.

Emulating the Effective Ankle Stiffness of Commercial Prosthetic Feet Using a Robotic Prosthetic Foot Emulator

Prosthetic foot selection for individuals with lower limb amputation relies primarily on clinician judgment. The prosthesis user rarely has an opportunity to provide experiential input into the decision by trying different feet. A prosthetic foot emulator (PFE) is a robotic prosthetic foot that could facilitate prosthesis users' ability to trial feet with different mechanical characteristics. Here, we introduce a procedure by which a robotic PFE is configured to emulate the sagittal plane effective ankle stiffness of a range of commercial prosthetic forefeet. Mechanical testing was used to collect data on five types of commercial prosthetic feet across a range of foot sizes and intended user body weights. Emulated forefoot profiles were parameterized using Bezier curve fitting on ankle torque-angle data. Mechanical testing was repeated with the PFE, across a subset of emulated foot conditions, to assess the accuracy of the emulation. Linear mixed-effects regression and Bland-Altman Limits of Agreement analyses were used to compare emulated and commercial ankle torque-angle data. Effective ankle stiffness of the emulated feet was significantly associated with the corresponding commercial prosthetic feet (p<.001). On average, the emulated forefeet reproduced the effective ankle stiffness of corresponding commercial feet within 1%. Furthermore, differences were independent of prosthetic foot type, foot size, or user body weight. These findings suggest a PFE could be an effective tool for emulating commercial prosthetic feet, enabling prosthesis users to quickly trial different feet and provide experiential input as part of a prosthetic foot prescription.

A prospective assessment of an adjustable, immediate fit, subischial transfemoral prosthesis

Objective

To assess the feasibility of an adjustable, subischial transfemoral prosthesis by comparing self-reported outcome measures regarding socket comfort, fit and utility relative to a persons’ conventionally made socket. Assessing limb compressibility was another aim of this study.

Design

A single-group pre-post intervention design.

Setting

Physical medicine and rehabilitation biomechanics laboratory.

Participants

All 18 enrolled participants (N = 18) completed the feasibility trial. There were 16 men and 2 women with an average age of 59.4 (±7) years. Most of the participants (61.1%) had worn a socket for 1 to 10 years before the trial, 22.2% of the participants had worn one for less than a year, and 16.7% of the participants had worn a prosthesis for more than 10 years.

Intervention

Participants were fit with the study prosthesis and used it for a 2-week home trial.

Main Outcome Measures

A Prosthetic Comfort and Utility Questionnaire was completed on the participant's conventional prosthetic device and the subischial socket system after the trial.

Results

The adjustable subischial prostheses were rated superior overall to the participant's conventional sockets (40.9 ± 7.2 vs 32.8 ± 10.8; P=.004). Six of the 10 parameters measured (adjustability, overall fit, prosthesis weight, sitting comfort, standing comfort, and standing stability) were rated higher for the adjustable prostheses compared to the conventional sockets. Compression of the soft tissues of the thigh ranged from 5.6 ± 4.2 cm at the distal end to 7.3 ± 3.6 cm at the proximal site. There were no falls, skin breakdown, or limb ischemia. At the 2-month telephone follow-up, 61% of subjects had transitioned to using the adjustable subischial socket most of the time.

Conclusions

The adjustable, immediate fit, subischial prosthesis provided safe, comfortable, and functional ambulation for persons with transfemoral limb loss in this short-term feasibility study. This study supports the consideration of a new paradigm in transfemoral prosthetics—adjustable subischial sockets. These devices should be tested in a larger multi-center study.

Reported Outcome Measures in Studies of Real-World Ambulation in People with a Lower Limb Amputation: A Scoping Review

BACKGROUND

The rapidly increasing use of wearable technology to monitor free-living ambulatory behavior demands to address to what extent the chosen outcome measures are representative for real-world situations. This scoping review aims to provide an overview of the purpose of use of wearable activity monitors in people with a Lower Limb Amputation (LLA) in the real world, to identify the reported outcome measures, and to evaluate to what extent the reported outcome measures capture essential information from real-world ambulation of people with LLA.

METHODS

The literature search included a search in three databases (MEDLINE, CINAHL, and EMBASE) for articles published between January 1999 and January 2022, and a hand-search.

RESULTS AND CONCLUSIONS

98 articles met the inclusion criteria. According to the included studies' main objective, the articles were classified into observational (n = 46), interventional (n = 34), algorithm/method development (n = 12), and validity/feasibility studies (n = 6). Reported outcome measures were grouped into eight categories: step count (reported in 73% of the articles), intensity of activity/fitness (31%), type of activity/body posture (27%), commercial scores (15%), prosthetic use and fit (11%), gait quality (7%), GPS (5%), and accuracy (4%). We argue that researchers should be more careful with choosing reliable outcome measures, in particular, regarding the frequently used category step count. However, the contemporary technology is limited in providing a comprehensive picture of real-world ambulation. The novel knowledge from this review should encourage researchers and developers to engage in debating and defining the framework of ecological validity in rehabilitation sciences, and how this framework can be utilized in the development of wearable technologies and future studies of real-world ambulation in people with LLA.

Finite element modeling of an energy storing and return prosthetic foot and implications of stiffness on rollover shape

Energy storing and return (ESAR) prosthetic feet showed continuous improvements during the last 30 years. Despite this, standard guidelines are still missing to achieve an optimal foot design in terms of performances. One of the most important design parameters in ESAR feet is the Rollover Shape (RoS). This represents the foot Center of Pressure (CoP) path in a shank-based coordinate system during stance. RoS objectively describes the foot behavior according to its stiffness, which depends on foot geometry and material. This work presents the development of a finite element modeling methodology able to predict the stiffness characteristic of an ESAR foot and its RoS. The validation of the model is performed on a well-known commercially available prosthetic foot both in bench tests and realistic walking scenario. The obtained results confirm an error of +6.1% on stiffness estimation and +10.2% on RoS evaluation, which underlines that the proposed method is a powerful tool able to replicate the mechanical behavior of a prosthetic foot.

Trends and Opportunities in Health Economic Evaluations of Prosthetic Care Innovations

Overcoming obstacles to prosthetic fittings requires frequent tryouts of sockets and components. Repetitions of interventions are upsetting for users and place substantial economic burden on healthcare systems. Encouraging prosthetic care innovations capable of alleviating clinical and financial shortcomings of socket-based solutions is essential. Nonetheless, evidence of socio-economic benefits of an innovation are required to facilitate access to markets. Unfortunately, complex decisions must be made when allocating resources toward the most relevant health economic evaluation (HEE) at a given stage of development of an innovation. This paper first, aimed to show the importance and challenges of HEEs of intervention facilitating prosthetic fittings. Next, the main trends in HEEs at various phases of product development and clinical acceptance of prosthetic care innovations were outlined. Then, opportunities for a basic framework of a preliminary cost-utility analysis (CUA) during the mid-stage of development of prosthetic care innovations were highlighted. To do this, fundamental and applied health economic literature and prosthetic-specific publications were reviewed to extract and analyse the trends in HEEs of new medical and prosthetic technologies, respectively. The findings show there is consensus around the weaknesses of full CUAs (e.g., lack of timeliness, resource-intensive) and strengths of preliminary CUAs (e.g., identify evidence gaps, educate design of full CUA, fast-track approval). However, several obstacles must be overcome before preliminary CUA of prosthetic care innovations will be routinely carried out. Disparities of methods and constructs of usual preliminary CUA are barriers that could be alleviated by a more standardized framework. The paper concludes by identifying that there are opportunities for the development of a basic framework of preliminary CUA of prosthetic care innovations. Ultimately, the collaborative design of a framework could simplify selection of the methods, standardise outcomes, ease comparisons between innovations and streamline pathways for adoption. This might facilitate access to economical solutions that could improve the life of individuals suffering from limb loss.

Functional performance differences between carbon fiber and fiberglass prosthetic feet

BACKGROUND

Persons with lower limb amputation require increased functionality. The largest category of feet for active individuals with a transtibial amputation is energy storage and return (ESR) feet. These feet are typically constructed of carbon fiber composite materials. Recently, a prosthetic foot composed of a fiberglass composite has emerged in the market. However, there are no comparative studies of these devices.

OBJECTIVES

Compare the biomechanical performance and prosthesis-related quality of life when using a fiberglass prosthetic foot design compared with traditional carbon fiber ESR designs.

STUDY DESIGN

This is a repeated-measures randomized cross-over trial.

METHODS

Gait analysis was performed on 10 experienced male subjects with unilateral transtibial amputations (K-level III) while walking on level ground and a ramp. Patient-reported outcomes were collected using the Prosthesis Evaluation Questionnaire.

RESULTS

Gait data demonstrated increased ankle dorsiflexion (P < .01), similar ankle moments (P = .07), and increased ankle power generation (P = .01) when using the fiberglass foot. The increased power generation occurred at the correct time in the gait cycle such that the timing and magnitude of peak knee flexion was unaffected (P > .19). The fiberglass foot had greater energy absorption during gait (P = .01) with no difference in energy return (P = .37). The subjects expressed improved prosthesis-related quality of life with the fiberglass foot (P = .01).

CONCLUSIONS

The findings of this study demonstrate that the new ESR foot comprising a fiberglass material had better performance than traditional designs using a carbon fiber material.

STEPFORWARD study: a randomised controlled feasibility trial of a self-aligning prosthetic ankle-foot for older patients with vascular-related amputations

OBJECTIVES

To determine the feasibility of conducting a full-scale randomised controlled trial (RCT) of the effectiveness and cost-effectiveness of a self-aligning prosthetic ankle-foot compared with a standard prosthetic ankle-foot.

DESIGN

Multicentre parallel group feasibility RCT.

SETTING

Five prosthetics centres in England recruiting from July 2018 to August 2019.

PARTICIPANTS

Adults aged ≥50 years with a vascular-related or non-traumatic transtibial amputation for 1 year or longer, categorised as having 'limited community mobility' and using a non-self-aligning ankle-foot.

INTERVENTION

Participants were randomised into one of two groups for 12 weeks: self-aligning prosthetic ankle-foot or existing non-self-aligning prosthetic ankle-foot.

OUTCOMES

Feasibility measures: recruitment, consent and retention rates; and completeness of questionnaire and clinical assessment datasets across multiple time points. Feasibility of collecting daily activity data with wearable technology and health resource use data with a bespoke questionnaire.

RESULTS

Fifty-five participants were randomised (61% of the target 90 participants): n=27 self-aligning ankle-foot group, n=28 non-self-aligning ankle-foot group. Fifty-one participants were included in the final analysis (71% of the target number of participants). The consent rate and retention at final follow-up were 86% and 93%, respectively. The average recruitment rate was 1.25 participants/site/month (95% CI 0.39 to 2.1). Completeness of questionnaires ranged from 89%-94%, and clinical assessments were 92%-95%, including the activity monitor data. The average completion rates for the EQ-5D-5L and bespoke resource use questionnaire were 93% and 63%, respectively.

CONCLUSIONS

This feasibility trial recruited and retained participants who were categorised as having 'limited community mobility' following a transtibial amputation. The high retention rate of 93% indicated the trial was acceptable to participants and feasible to deliver as a full-scale RCT. The findings support a future, fully powered evaluation of the effectiveness and cost-effectiveness of a self-aligning prosthetic ankle-foot compared with a standard non-self-aligning version with some adjustments to the trial design and delivery.

TRIAL REGISTRATION NUMBER

ISRCTN15043643.

Focusing research efforts on the unique needs of women prosthesis users

Introduction

Women with lower limb loss represent a relevant and growing patient cohort with unique rehabilitation needs. These needs are emphasized in a growing body of literature and the most recent Veteran Affairs/Department of Defense clinical practice guidelines.

Prosthetics Challenges

Women with limb loss experience greater dissatisfaction with prosthetic fit, appearance, and types of footwear they can use. There is a lack of prosthetics solutions to accommodate the desire of women to wear different footwear varieties, including high heels. The choice to wear a variety of footwear is important to attire and hence community participation. Despite these recognized challenges, women are still underserved in prosthetics research, which limits available information to guide the rehabilitation process.

Research Initiatives

This narrative review describes considerations of lower limb prosthesis prescription and use by women, and examples of current research to address these topics. Research efforts are beginning to explore factors that contribute to prosthetics prescription for women, and design creative prosthetics solutions to expand the range of available footwear options. Research is still needed to characterize the types of footwear women with limb loss prefer to use, and the effects of prosthesis designs, footwear, and lower limb loss on women mobility outcomes and community participation.

Conclusions

Through targeted research initiatives, scientists and clinicians can be responsive to the specific needs of women to provide evidence-based guidelines for prosthetics prescription and improve the patient-centered care after limb loss.

The effect of prosthetic foot stiffness on foot-ankle biomechanics and relative foot stiffness perception in people with transtibial amputation

BACKGROUND

Prosthetic feet are available in a range of stiffness categories, however, there is limited evidence to guide optimal selection during prosthetic foot prescription. The aim of this study was to determine the effect of commercial prosthetic foot stiffness category on foot-ankle biomechanics, gait symmetry, community ambulation, and relative foot stiffness perception.

METHODS

Participants were fit in randomized order with three consecutive stiffness categories of a commonly-prescribed prosthetic foot. Prosthetic foot roll-over shape and ankle push-off power and work were determined via data collected during walking in a motion analysis laboratory. Step activity was recorded during community use of each foot. Self-reported perception of relative foot stiffness was assessed with an ad hoc survey.

FINDINGS

Seventeen males with transtibial amputation completed the study. Prosthetic foot roll-over radius increased with increased prosthetic foot stiffness categories (p < 0.001). Both prosthetic ankle push-off peak power and work decreased with increased foot stiffness categories (p = 0.002). There was no association between prosthetic foot stiffness category and step length symmetry or steps per day. When assessed post-accommodation, there was no association between relative foot stiffness perception and the stiffness category across prosthetic foot conditions.

INTERPRETATION

Prosthetic foot stiffness category was significantly associated with changes in prosthetic foot-ankle biomechanical variables, however, was not associated with changes in gait symmetry or community ambulation. Relative prosthetic foot stiffness perception after accommodation was generally inconsistent with the order of prosthetic foot stiffness categories.

CLINICAL RELEVANCE

While there were quantifiable differences in prosthetic foot-ankle biomechanics across stiffness categories, no significant differences were detected in gait symmetry or mean daily step count in the community. Furthermore, after community use, participants perceptions of relative stiffness across feet were generally inconsistent with the order of prosthetic foot stiffness categories. These findings raise questions as to whether changes in commercial prosthetic foot stiffness category (within a clinically relevant range) affect subjective and objective measures relevant to successful outcomes from prosthetic foot prescription.

Maximal Walking Distance in Persons with a Lower Limb Amputation

The distance one can walk at a time could be considered an important functional outcome in people with a lower limb amputation. In clinical practice, walking distance in daily life is based on self-report (SIGAM mobility grade (Special Interest Group in Amputee Medicine)), which is known to overestimate physical activity. The aim of this study was to assess the number of consecutive steps and walking bouts in persons with a lower limb amputation, using an accelerometer sensor. The number of consecutive steps was related to their SIGAM mobility grade and to the consecutive steps of age-matched controls in daily life. Twenty subjects with a lower limb amputation and ten age-matched controls participated in the experiment for two consecutive days, in their own environment. Maximal number of consecutive steps and walking bouts were obtained by two accelerometers in the left and right trouser pocket, and one accelerometer on the sternum. In addition, the SIGAM mobility grade was determined and the 10 m walking test (10 MWT) was performed. The maximal number of consecutive steps and walking bouts were significantly smaller in persons with a lower limb amputation, compared to the control group (p < 0.001). Only 4 of the 20 persons with a lower limb amputation had a maximal number of consecutive steps in the range of the control group. Although the maximal covered distance was moderately correlated with the SIGAM mobility grade in participants with an amputation (r = 0.61), for 6 of them, the SIGAM mobility grade did not match with the maximal covered distance. The current study indicated that mobility was highly affected in most persons with an amputation and that the SIGAM mobility grade did not reflect what persons with a lower limb amputation actually do in daily life. Therefore, objective assessment of the maximal number of consecutive steps of maximal covered distance is recommended for clinical treatment.

Speed Adaptable Prosthetic Foot: Concept Description, Prototyping and Initial User Testing

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.

Technology for monitoring everyday prosthesis use: a systematic review

BACKGROUND

Understanding how prostheses are used in everyday life is central to the design, provision and evaluation of prosthetic devices and associated services. This paper reviews the scientific literature on methodologies and technologies that have been used to assess the daily use of both upper- and lower-limb prostheses. It discusses the types of studies that have been undertaken, the technologies used to monitor physical activity, the benefits of monitoring daily living and the barriers to long-term monitoring, with particular focus on low-resource settings.

METHODS

A systematic literature search was conducted in PubMed, Web of Science, Scopus, CINAHL and EMBASE of studies that monitored the activity of prosthesis users during daily-living.

RESULTS

Sixty lower-limb studies and 9 upper-limb studies were identified for inclusion in the review. The first studies in the lower-limb field date from the 1990s and the number has increased steadily since the early 2000s. In contrast, the studies in the upper-limb field have only begun to emerge over the past few years. The early lower-limb studies focused on the development or validation of actimeters, algorithms and/or scores for activity classification. However, most of the recent lower-limb studies used activity monitoring to compare prosthetic components. The lower-limb studies mainly used step-counts as their only measure of activity, focusing on the amount of activity, not the type and quality of movements. In comparison, the small number of upper-limb studies were fairly evenly spread between development of algorithms, comparison of everyday activity to clinical scores, and comparison of different prosthesis user populations. Most upper-limb papers reported the degree of symmetry in activity levels between the arm with the prosthesis and the intact arm.

CONCLUSIONS

Activity monitoring technology used in conjunction with clinical scores and user feedback, offers significant insights into how prostheses are used and whether they meet the user's requirements. However, the cost, limited battery-life and lack of availability in many countries mean that using sensors to understand the daily use of prostheses and the types of activity being performed has not yet become a feasible standard clinical practice. This review provides recommendations for the research and clinical communities to advance this area for the benefit of prosthesis users.

Deformable link segment analysis for prosthetic foot-ankle components: Kinematics

Approaches in the literature for estimating prosthetic foot-ankle power typically require calculating the segment deformation velocity. This, in turn, necessitates approximating the segment angular velocity. Methods can be distinguished by the way in which a segment is defined and the assumptions used for estimating the segment angular velocity. However, isolating foot-ankle performance from overall prosthetic system performance is limited by uncertainties in the definition of angular velocity of a deformable segment. A deformable link segment (DLS) analysis is proposed that provides a means for estimating deformation velocity of a deformable segment without first approximating the angular velocity: the deformation velocity and angular velocity are solved simultaneously at each instant during the stance phase of gait. DLS analysis was compared to two approaches in the literature: the distal foot (DF) model and the unified deformable (UD) segment model during over-ground walking for three trans-tibial prosthesis users. DLS and UD segment estimates of deformation velocity were comparable when applied to the UD segment. Furthermore, DLS analysis enables modelling of deformable prosthetic foot-ankle components separately from other prosthetic componentry. The method is proposed as a rigorous approach to estimating angular velocity and deformation velocity of passive prosthetic foot-ankle components for subsequent calculation of deformation power and energy performance of these devices.

A more compliant prosthetic foot better accommodates added load while walking among Servicemembers with transtibial limb loss

Selecting an optimal prosthetic foot is particularly challenging for highly active individuals with limb loss, such as military personnel, who need to seamlessly perform a variety of demanding activities/tasks (often with and without external loads) while minimizing risk of musculoskeletal injuries over the longer term. Here, we expand on prior work by comparing biomechanical and functional outcomes in two prosthetic feet with the largest differences in mechanical response to added load (i.e., consistently "Compliant" and "Stiff" forefoot properties). In each foot, fourteen male Servicemembers with unilateral transtibial limb loss (from trauma) completed instrumented gait analyses in all combinations of two loading conditions (with and without 22 kg weighted vest) and two walking speeds (1.34 and 1.52 m/s), as well as the Prosthesis Evaluation Questionnaire. With the Stiff foot, sound limb peak loading was 2% smaller (p = 0.043) in the loaded versus unloaded condition, but similar between loading conditions in the Compliant foot (note, the Stiff foot was associated with larger loads, overall). Independent of load or walking speed, the Compliant (versus Stiff) foot provided 67.9% larger (p < 0.001) prosthetic push-off, 17.7% larger (p = 0.01) roll-over shape radii, and was subjectively favored by 10 participants. A more Compliant versus Stiff prosthetic foot therefore appears to better accommodate walking with and without added load, and reinforce the notion that mechanical properties of prosthetic feet should be considered for near-term performance and longer-term (joint) health.

Loading characteristics data applied on osseointegrated implant by transfemoral bone-anchored prostheses fitted with basic components during daily activities

The data in this paper are related to the research articles entitled “Kinetics of transfemoral amputees with osseointegrated fixation performing common activities of daily living” (Lee et al., Clinical Biomechanics, 2007.22(6). p. 665–673) and “Magnitude and variability of loading on the osseointegrated implant of transfemoral amputees during walking” (Lee et al., Med Eng Phys, 2008.30(7). p. 825–833). This article contains the overall and individual loading characteristics applied on screw-type osseointegrated implant generated by transfemoral bone-anchored prostheses fitted with basic components during daily activities at self-selected comfortable pace. Overall and individual data was presented for the (A) spatio-temporal characteristics, (B) loading patterns, (C) loading boundaries and (D) the loading local extremum during level walking, ascending and descending ramp and stairs. Inter-participant variability of these new datasets with basic components is critical to improve the efficacy and safety of prosthetic components as well as the design of future automated algorithms and clinical trials. Online repository contains the files: https://data.mendeley.com/datasets/hh8rjjh73w/1.

Mobility analysis of AmpuTees (MAAT 5): Impact of five common prosthetic ankle-foot categories for individuals with diabetic/dysvascular amputation

Introduction

Diabetes and vascular disease represent the most common etiologies for lower limb amputations. In lower limb loss rehabilitation, the prosthetic ankle-foot mechanism is the most common major component needed to restore function. The purpose of this study was to examine the impact of five common prosthetic ankle-foot mechanisms on functional mobility in a large sample of individuals with amputation due to diabetes/dysvascular disease.

Methods

A retrospective analysis of the Prosthetic Limb Users' Survey of Mobility (PLUS-M®) captured in the patient care setting. A total of 738 individuals were included and subsequently subdivided into five groups based on the ankle-foot mechanism of their current prosthesis. Groups were compared using a general linear univariate model with age, body mass index, comorbid health status, time since amputation, and amputation level entered as covariates.

Results

The microprocessor ankle-foot group had the highest mobility (F_4,728 = 3.845, p=0.004), which was followed by the vertical loading pylon type ankle-foot, the hydraulic ankle-foot, the flex-walk-type ankle-foot, and lastly the flex-foot-type ankle-foot.

Conclusion

These results demonstrate that the selection of different prosthetic ankle-foot technology directly impacts functional mobility for the patient with an amputation due to diabetes and/or vascular disease.

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

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.

Analyzing Gait in the Real World Using Wearable Movement Sensors and Frequently Repeated Movement Paths

Assessing interventions for mobility disorders using real-life movement remains an unsolved problem. We propose a new method combining the strengths of traditional laboratory studies where environment is strictly controlled, and field-based studies where subjects behave naturally. We use a foot-mounted inertial sensor, a GPS receiver and a barometric altitude sensor to reconstruct a subject's path and detailed foot movement, both indoors and outdoors, during days-long measurement using strapdown navigation and sensor fusion algorithms. We cluster repeated movement paths based on location, and propose that on these paths, most environmental and behavioral factors (e.g., terrain and motivation) are as repeatable as in a laboratory. During each bout of movement along a frequently repeated path, any synchronized measurement can be isolated for study, enabling focused statistical comparison of different interventions. We conducted a 10-day test on one subject wearing athletic shoes and sandals each for five days. The algorithm detected four frequently-repeated straight walking paths with at least 300 total steps and repetitions on at least three days for each condition. Results on these frequently-repeated paths indicated significantly lower foot clearance and shorter stride length and a trend toward decreased stride width when wearing athletic shoes vs. sandals. Comparisons based on all straight walking were similar, showing greater statistical power, but higher variability in the data. The proposed method offers a new way to evaluate how mobility interventions affect everyday movement behavior.

Prosthesis satisfaction in lower limb amputees: A systematic review of associated factors and questionnaires

BACKGROUND

Factors influencing patient satisfaction with a transtibial prosthesis have been studied fragmentarily. The aims of this systematic review were to review the literature regarding factors of influence on patient satisfaction with a transtibial prosthesis, to report satisfaction scores, to present an overview of questionnaires used to assess satisfaction and examine how these questionnaires operationalize satisfaction.

METHODS

A literature search was performed in PubMed, Embase, PsycInfo, CINAHL, Cochrane, and Web of Knowledge databases up to February 2018 to identify relevant studies.

RESULTS

Twelve of 1832 studies met the inclusion criteria. Sample sizes ranged from 14 to 581 participants, mean age ranged from 18 to 70 years, and time since amputation ranged from 3 to 39 years. Seven questionnaires assessed different aspects of satisfaction. Patient satisfaction was influenced by appearance, properties, fit, and use of the prosthesis, as well as aspects of the residual limb. These influencing factors were not relevant for all amputee patients and were related to gender, etiology, liner use, and level of amputation. No single factor was found to significantly influence satisfaction or dissatisfaction. Significant associations were found between satisfaction and gender, etiology, liner use, and level of amputation.

CONCLUSION

Relevance of certain factors for satisfaction was related to specific amputee patient groups. Questionnaires assessing satisfaction use different operationalizations, making comparisons between studies difficult.

Benefits of an increased prosthetic ankle range of motion for individuals with a trans-tibial amputation walking with a new prosthetic foot

BACKGROUND

Individuals with trans-tibial amputation show a greater peak prosthetic ankle power (push- off) when using energy storing and returning (ESAR) prosthetic feet as compared to solid-ankle cushion-heel feet. ESAR feet further contribute to the users' body support and thus limit prosthetic ankle motion. To improve ankle motion, articulating prosthetic feet have been introduced. However, articulating feet may diminish push-off.

RESEARCH QUESTION

Does a novel prosthetic foot, with a serial layout of carbon fibre leaf springs, connected by a multi-centre joint construction, have advantages in kinematics and kinetics over a conventional ESAR prosthetic foot?> METHODS: Eleven individuals with unilateral trans-tibial amputation were fitted with the novel foot (NF) and a conventional ESAR Foot (CF) and underwent 3D gait analysis. As an additional power estimate of the prosthetic ankle, a unified, deformable, segment model approach was applied. Eleven matched individuals without impairments served as a reference.

RESULTS

The NF shows an effective prosthetic ankle range of motion that is closer to a physiologic ankle range of motion, at 31.6° as compared to 15.2° with CF (CF vs. NF p = 0.003/NF vs. Reference p = 0.171) without reducing the maximum prosthetic ankle joint moment. Furthermore, the NF showed a great increase in prosthetic ankle power (NF 2.89 W/kg vs. CF 1.48 W/kg CF vs. NF p = <0.001) and a reduction of 19% in the peak knee varus moment and 13% in vertical ground reaction forces on the sound side for NF in comparison to CF.

SIGNIFICANCE

The NF shows that serial carbon fibre leaf springs, connected by a multi-centre joint construction gives a larger ankle joint range of motion and higher ankle power than a conventional carbon fibre structure alone. Consequently load is taken off the contralateral limb, as measured by the decrease in vertical ground reaction forces and peak knee varus moment.

Confirmation bias affects user perception of knee braces

Technological advances in orthopedic devices such as prostheses and orthoses are intended to improve function but may also result in increased complexity and expense. Consequently, accurate determination of effectiveness is important. When devices with advanced technology are used, it is possible that confirmation bias - the tendency for a user to actually experience what he or she expects to experience - will influence outcomes. This study assessed confirmation bias in 18 healthy young adults walking in knee braces. Participants wore two identical braces, but one was cosmetically modified and participants were told that it was a prototype computerized brace that could dynamically alter its stiffness. Before using the braces, the majority of users indicated a preference for the "computerized" brace. Actual walking showed no differences between the two braces. Following walking, users maintained preference for the "computerized" brace, indicating the presence of confirmation bias. These results underscore the importance of blinding when self-reported outcomes are used and the need to consider a placebo effect when comparing orthopedic devices.

Comparison between three types of prosthetic feet: a randomized double-blind single-subject multiple-rater trial

There are many prosthetic feet (Pfeet) on the market, and those in the same category do not necessarily have the same properties. We assessed three different Pfeet in terms of gait patterns on various terrains, balance and walking speed in a randomized double-blind controlled single-subject multiple-rater clinical trial. The patient was a 43-year old man who was an active prosthesis user and was amputated at transtibial level because of injury 17 years ago. One Solid Ankle Cushion Heel and two Dynamic Elastic Response (DER) Pfeet were tried six times in random order. The patient walked on flat, uneven, sloped terrain and stairs. Gait pattern was rated in comparison with the patient's previous prosthetic foot (Pfoot) by a physiatrist, physiotherapist, prosthetist and the patient; one-leg standing test on the prosthesis and 10-m walking test were also performed. The ratings differed significantly between the raters on each terrain, and there was no agreement among the raters regarding the ranking order of the Pfeet. All the Pfeet were generally rated as worse than the patient's previous one. The patient gave lower ratings on average than the professionals and recognized the order of the tested Pfeet. The results of one-leg standing test with one DER and the Solid Ankle Cushion Heel Pfoot were statistically significant better than with the other DER and the patient's previous Pfoot. Our study therefore indicates that rehabilitation professionals, when blinded, cannot always reliably observe differences in walking on different terrains with different Pfeet. The patient may feel the differences, but those may not match what the manufacturers declare.

The effects of common footwear on stance-phase mechanical properties of the prosthetic foot-shoe system

BACKGROUND

Prosthetic feet are prescribed based on their mechanical function and user functional level. Subtle changes to the stiffness and hysteresis of heel, midfoot, and forefoot regions can influence the dynamics and economy of gait in prosthesis users. However, the user's choice of shoes may alter the prosthetic foot-shoe system mechanical characteristics, compromising carefully prescribed and rigorously engineered performance of feet.

OBJECTIVES

Observe the effects of footwear on the mechanical properties of the prosthetic foot-shoe system including commonly prescribed prosthetic feet.

STUDY DESIGN

Repeated-measures, Mechanical characterization.

METHODS

The stiffness and energy return was measured using a hydraulic-driven materials test machine across combinations of five prosthetic feet and four common shoes as well as a barefoot condition.

RESULTS

Heel energy return decreased by an average 4%-9% across feet in all shoes compared to barefoot, with a cushioned trainer displaying the greatest effect. Foot designs that may improve perceived stability by providing low heel stiffness and rapid foot-flat were compromised by the addition of shoes.

CONCLUSION

Shoes altered prosthesis mechanical characteristics in the sagittal and frontal planes, suggesting that shoe type should be controlled or reported in research comparing prostheses. Understanding of how different shoes could alter certain gait-related characteristics of prostheses may aid decisions on footwear made by clinicians and prosthesis users. Clinical relevance Shoes can alter function of the prosthetic foot-shoe system in unexpected and sometimes undesirable ways, often causing similar behavior across setups despite differences in foot design, and prescribing clinicians should carefully consider these effects on prosthesis performance.

Laboratory- and community-based health outcomes in people with transtibial amputation using crossover and energy-storing prosthetic feet: A randomized crossover trial

Contemporary prosthetic feet are generally optimized for either daily or high-level activities. Prosthesis users, therefore, often require multiple prostheses to participate in activities that span a range of mobility. Crossover feet (XF) are designed to increase the range of activities that can be performed with a single prosthesis. However, little evidence exists to guide clinical prescription of XF relative to traditional energy storing feet (ESF). The objective of this study was to assess the effects of XF and ESF on health outcomes in people with transtibial amputation. A randomized crossover study was conducted to assess changes in laboratory-based (endurance, perceived exertion, walking performance) and community-based (step activity and self-reported mobility, fatigue, balance confidence, activity restrictions, and satisfaction) outcomes. Twenty-seven participants were fit with XF and ESF prostheses with standardized sockets, interfaces, and suspensions. Participants were not blinded to the intervention, and wore each prosthesis for one month while their steps were counted with an activity monitor. After each accommodation period, participants returned for data collection. Endurance and perceived exertion were measured with the Six-Minute Walk Test and Borg-CR100, respectively. Walking performance was measured using an electronic walkway. Self-reported mobility, fatigue, balance confidence, activity restrictions, and satisfaction were measured with survey instruments. Participants also reported foot preferences upon conclusion of the study. Differences between feet were assessed with a crossover analysis. While using XF, users experienced improvements in most community-based outcomes, including mobility (p = .001), fatigue (p = .001), balance confidence (p = .005), activity restrictions (p = .002), and functional satisfaction (p < .001). Participants also exhibited longer sound side steps in XF compared to ESF (p < .001). Most participants (89%) reported an overall preference for XF; others (11%) reported no preference. Results indicate that XF may be a promising alternative to ESF for people with transtibial amputation who engage in a range of mobility activities.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02440711.

Prosthetic energy return during walking increases after 3 weeks of adaptation to a new device

Background

There are many studies that have investigated biomechanical differences among prosthetic feet, but not changes due to adaptation over time. There is a need for objective measures to quantify the process of adaptation for individuals with a transtibial amputation. Mechanical power and work profiles are a primary focus for modern energy-storage-and-return type prostheses, which strive to increase energy return from the prosthesis. The amount of energy a prosthesis stores and returns (i.e., negative and positive work) during stance is directly influenced by the user’s loading strategy, which may be sensitive to alterations during the course of an adaptation period. The purpose of this study was to examine changes in lower limb mechanical work profiles during walking following a three-week adaptation to a new prosthesis.

Methods

A retrospective analysis was performed on 22 individuals with a unilateral transtibial amputation. Individuals were given a new prosthesis at their current mobility level (K3 or above) and wore it for three weeks. Kinematic and kinetic measures were recorded from overground walking at 0, 1.5, and 3 weeks into the adaptation period at a self-selected pace. Positive and negative work done by the prosthesis and sound ankle-foot were calculated using a unified deformable segment model and a six-degrees-of-freedom model for the knee and hip.

Results

Positive work from the prosthesis ankle-foot increased by 6.1% and sound ankle-foot by 5.7% after 3 weeks (p = 0.041, 0.036). No significant changes were seen in negative work from prosthesis or sound ankle-foot (p = 0.115, 0.192). There was also a 4.1% increase in self-selected walking speed after 3 weeks (p = 0.038). Our data exhibited large inter-subject variations, in which some individuals followed group trends in work profiles while others had opposite trends in outcome variables.

Conclusions

After a 3-week adaptation, 14 out of 22 individuals with a transtibial amputation increased energy return from the prosthesis. Such findings could indicate that individuals may better utilize the spring-like function of the prosthesis after an adaptation period.

Electronic supplementary material

The online version of this article (10.1186/s12984-018-0347-1) contains supplementary material, which is available to authorized users.

When to biomechanically examine a lower-limb amputee: A systematic review of accommodation times

BACKGROUND

Hundreds of investigations examining biomechanical outcomes of various prostheses have been completed, but one question remains unanswered: how much time should an amputee be given to accommodate to a new prosthesis prior to biomechanical testing?

OBJECTIVE

To examine the literature for accommodation time given during biomechanical investigations to determine whether consensus exists.

STUDY DESIGN

Systematic review.

METHODS

A systematic search was completed on 7 January 2016 using PubMed and Scopus.

RESULTS

The search resulted in 156 investigations. Twenty-eight studies did not provide an accommodation or were unclear (e.g. provided a "break in period"), 5 studies tested their participants more than once, 25 tested only once and on the same day participants received a new prosthesis (median (range): above-knee: 60 (10-300) min; below-knee: 18 (5-300) min), and 98 tested once and gave a minimum of 1 day for accommodation (hip: 77 (60-180) days; above-knee: 42 (1-540) days; below-knee: 21 (1-475) days).

CONCLUSION

The lack of research specifically examining accommodation and the high variability in this review's results indicates that it remains undecided how much accommodation is necessary. There is a need for longitudinal biomechanical investigations to determine how outcomes change as amputees accommodate to a new prosthesis. Clinical relevance The results of this review indicate that little research has been done regarding lower-limb amputees accommodating to a new prosthesis. Improper accommodation could lead to increased variability in results, results that are not reflective of long-term use, and could cause clinicians to make inappropriate decisions regarding a prosthesis.

Instantaneous stiffness and hysteresis of dynamic elastic response 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 relevance The quantitative stiffness and hysteresis data from this study can be used by prosthetists to aid the prescription process and make it more objective.

Sensitivity of biomechanical outcomes to independent variations of hindfoot and forefoot stiffness in foot prostheses

Many studies have reported the effects of different foot prostheses on gait, but most results cannot be generalized because the prostheses' properties are seldom reported. We varied hindfoot and forefoot stiffness in an experimental foot prosthesis, in increments of 15N/mm, and tested the parametric effects of these variations on treadmill walking in unilateral transtibial amputees, at speeds from 0.7 to 1.5m/s. We computed outcomes such as prosthesis energy return, center of mass (COM) mechanics, ground reaction forces, and joint mechanics, and computed their sensitivity to component stiffness. A stiffer hindfoot led to reduced prosthesis energy return, increased ground reaction force (GRF) loading rate, and greater stance-phase knee flexion and knee extensor moment. A stiffer forefoot resulted in reduced prosthetic-side ankle push-off and COM push-off work, and increased knee extension and knee flexor moment in late stance. The sensitivity parameters obtained from these tests may be useful in clinical prescription and further research into compensatory mechanisms of joint function.

The dead spot phenomenon in prosthetic gait: Quantified with an analysis of center of pressure progression and its velocity in the sagittal plane

BACKGROUND

The "dead spot" phenomenon in prosthetics is a disruption in forward progression observed in the rearfoot of passive prosthetic foot-ankle systems which results in a compensatory and inefficient gait pattern by amputees. A metric to quantify the dead spot as a kinetic event has not yet been introduced. The present study implements a three-part metric to evaluate the dead spot in terms of time, magnitude, and total area using center of pressure velocity and a novel threshold value calculation.

METHODS

The metrics are implemented for proof of efficacy using a convenient sample of four amputees (2 transtibial, 2 transfemoral) who walked in a 3D motion capture system with integrated force plates over five foot conditions.

FINDINGS

"Continuous-lever" feet designs showed the most favorable metric results between subjects (p<0.05) and in an ad hoc analysis compared to an ideal foot condition within subjects (p>0.05). Ten of 18 (55.6%) foot conditions found to be similar to the ideal were continuous-lever feet. Lack of significant similarity between the feet and ideal conditions (1 of 18, 5.6%) were found in transfemoral subjects.

INTERPRETATION

The metric calculations were able to show statistical difference among foot conditions between subjects. One foot (continuous-lever, glass composite) had no detectable dead spot in the transtibial subjects. The lack of significant findings in transfemoral subjects indicates a different coefficient in threshold calculations may be more appropriate for these subjects versus transtibial subjects. Further research with larger sample is needed to determine clinically significant findings among feet and between transtibial and transfemoral subjects.

The influence of passive-dynamic ankle-foot orthosis bending axis location on gait performance in individuals with lower-limb impairments

BACKGROUND

Passive-dynamic ankle-foot orthoses are commonly prescribed to augment impaired ankle muscle function, however their design and prescription are largely qualitative. One design includes a footplate and cuff, and flexible strut connecting the two. During gait, deflection occurs along the strut, with the greatest deflection at a central bending axis. The vertical location of the axis can affect lower extremity biomechanics. The goal of this study was to investigate the influence of bending axis location on gait performance.

METHODS

For thirteen participants with unilateral ankle muscle weakness, an additive manufacturing framework was used to fabricate passive-dynamic ankle-foot orthosis struts with central and off-center bending axes. Participants walked overground while electromyographic, kinetic and kinematic data were collected for three different bending axes: proximal (high), central (middle) and distal (low), and the participants indicated their order of bending axis preference after testing. Gait measures and preference effect sizes were examined during six regions of the gait cycle.

FINDINGS

A few differences between bending axes were observed: in the first double-leg support peak plantarflexion angle, peak dorsiflexion moment and positive hip work, in the early single-leg support peak knee extension moment and positive ankle and knee work, and in the late single-leg support gastrocnemius activity and vertical ground reaction force impulse. In addition, preference was strongly related to various gait measures.

INTERPRETATION

Despite the observed statistical differences, altering bending axis location did not produce large and consistent changes in gait performance. Thus, individual preference and comfort may be more important factors guiding prescription.