Evaluation of a Modified Running-specific Prosthetic Foot

Study Overview
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Brief Summary
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The goal of this study is to evaluate endurance, walking performance, mobility, and perceived exertion of transtibial prosthesis users (i.e., study participants) walking with a conventional energy storing prosthetic foot (ESF) and a novel modified running-specific prosthesis (mRSF). A randomized cross-over study will be conducted to determine if the mRSF provides superior performance to the ESF, which is commonly prescribed to most active individuals with lower limb amputation.

Detailed Description
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Amputation of a limb is a life-altering event with profound physical, psychological, and social implications. To address their functional, vocational, and recreational needs, people with lower limb amputation (LLA) are often provided with a prosthesis or artificial leg. While use of a prosthesis can allow an individual to achieve a basic level of functional mobility, absence of an anatomical foot and ankle still impairs their physical performance. As a result, people with LLA regularly exhibit decreased walking speeds, diminished endurance, and restricted ability to participate in desired life situations. Over the past three decades, increasingly sophisticated prosthetic foot designs have been developed by the prosthetics industry to replace amputated structures in the leg. Contemporary, energy storing feet (ESF) employ advanced materials and unique geometric designs to improve walking performance and endurance of their users. Although prosthetic limbs with ESF allow people with LLA the potential to return to an active lifestyle, even the most advanced ESF do not significantly reduce the increased energy demands required for walking when compared to conventional prosthetic feet. Commercially-available running-specific feet (RSF) like the Össur Cheetah (Össur, Reykjavik, Iceland) allow people with LLA to participate in athletic activities and sporting events. RSF provide significantly enhanced performance, compared to traditional ESF, by extending the length and increasing the stiffness of the prosthetic keel (forefoot). RSF also do not include a heel, as they are used only for running activities. Although transtibial runners with RSF exhibit endurance levels similar to non-amputees, the RSF design does not allow the biomechanical movements or provide the stability needed to use the foot for walking (over level or uneven terrain). A novel modified running-specific foot (mRSF) has been developed to integrate the performance of a RSF with the utility of an ESF. The mRSF combines the running keel (forefoot) of a RSF with the walking heel of a ESF. The mRSF can then be used for walking, running, and other routine daily activities. Preliminary feedback on the mRSF suggests that users experience improved overall function and high satisfaction with the device. However, empirical evidence is needed to support prescription of this prosthetic foot at other clinical facilities. The goal of this study is therefore to evaluate endurance, walking performance, mobility, and perceived exertion of transtibial prosthesis users (i.e., study participants) walking with a conventional ESF and the mRSF. Results will be compared to determine if the mRSF provides superior performance to the ESF, which is commonly prescribed to most active individuals with LLA.

Official Title
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Endurance, Energy Expenditure, Perceived Function, and Satisfaction of Persons With Transtibial Limb Loss Using a Running-Specific Prosthesis Modified for Walking

Conditions
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Transtibial Amputation

Intervention / Treatment
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* Device: Energy storing foot (ESF)
* Device: Modified running specific foot (mRSF)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: unilateral or bilateral, transtibial (below-knee) amputation from non-dysvascular causes Medicare functional classification level (K-level) 3 or higher (unlimited community ambulatory) prosthetic user for > 1 year scheduled to receive a mRSF prosthesis able and willing to participate in the study protocol (e.g., treadmill walking, overground walking, respond to survey questions, able to read and write English) Exclusion Criteria: contralateral lower or upper limb involvement any health condition that would limit participation in the study procedures (e.g., skin breakdown, heart disease)

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: mRSF-ESF<br>Study participants in Arm 1 will first receive the Modified running specific foot (mRSF) and then the Energy storing foot (ESF). Outcomes will be assessed (in each condition) after 1 month of use. Order of interventions will be randomly assigned. | Device: Energy storing foot (ESF)<br>* A commercially-available energy storing prosthetic foot<br>* Other names: Ossur Vari-flex;Device: Modified running specific foot (mRSF)<br>* A running specific prosthetic foot customized for both running and walking activities<br>* Other names: Ossur Cheetah (modified); Ossur Xplore;|
| Experimental: ESF-mRSF<br>Study participants in Arm 2 will first receive the Energy storing foot (ESF) and then the Modified running specific foot (mRSF). Outcomes will be assessed (in each condition) after 1 month of use. Order of interventions will be randomly assigned. | Device: Energy storing foot (ESF)<br>* A commercially-available energy storing prosthetic foot<br>* Other names: Ossur Vari-flex;Device: Modified running specific foot (mRSF)<br>* A running specific prosthetic foot customized for both running and walking activities<br>* Other names: Ossur Cheetah (modified); Ossur Xplore;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Metabolic Oxygen Consumption (VO2), Participants With Unilateral Amputation | Breath-by-Breath VO2 was collected as participants walked on a treadmill at self selected fast, normal, and slow speeds. Participants walked for 6 minutes at each speed (and in each experimental condition). VO2 was normalized energy expenditure to each participant's biological mass (i.e., body mass without prosthesis) Normalized VO2 data were averaged to produce 30-s values for minutes 3-6 of each trial. These 30-s values were used in for the described analyses. Both gross and net VO2 were examined, but produced similar results, so only gross VO2 results are reported. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Metabolic Oxygen Consumption (VO2), Participants With Bilateral Amputation | Breath-by-Breath VO2 was collected as participants walked on a treadmill at self selected fast, normal, and slow speeds. Participants walked for 6 minutes at each speed (and in each experimental condition). VO2 was normalized energy expenditure to each participant's biological mass (i.e., body mass without prosthesis) Normalized VO2 data were averaged to produce 30-s values for minutes 3-6 of each trial. These 30-s values were used in for the described analyses. Both gross and net VO2 were examined, but produced similar results, so only gross VO2 results are reported. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Six-minute Walk Test (6MWT), Participants With Unilateral Amputation | Participants were asked to walk as far as possible in 6 minutes. Participants walked around cones placed 30m apart in a level hallway. Total distance (in meters) walked in 6 minutes was recorded. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Six-minute Walk Test (6MWT), Participants With Bilateral Amputation | Participants were asked to walk as far as possible in 6 minutes. Participants walked around cones placed 30m apart in a level hallway. Total distance (in meters) walked in 6 minutes was recorded. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Borg Rating of Perceived Exertion (CR100), Participants With Unilateral Amputation | Participants were asked to self-report their level of perceived exertion after completing the 6MWT. Participants were shown the Borg CR100 rating scale and asked to identify their level of exertion on a scale ranging from 0 to 120. Higher scores mean greater exertion. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Borg Rating of Perceived Exertion (CR100), Participants With Bilateral Amputation | Participants were asked to self-report their level of perceived exertion after completing the 6MWT. Participants were shown the Borg CR100 rating scale and asked to identify their level of exertion on a scale ranging from 0 to 120. Higher scores mean greater exertion. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Walking Speed, Participants With Unilateral Amputation | Walking speed (m/s) was assessed with a 16-foot CIR GAITRite instrumented walkway while participants performed the 6-minute walk test (6MWT). | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Walking Speed, Participants With Bilateral Amputation | Walking speed (m/s) was assessed with a 16-foot CIR GAITRite instrumented walkway while participants performed the 6-minute walk test (6MWT). | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Step Width, Participants With Unilateral Amputation | Step width was assessed with a 16-foot CIR GAITRite instrumented walkway while participants performed the 6-minute walk test (6MWT). | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Step Width, Participants With Bilateral Amputation | Step width was assessed with a 16-foot CIR GAITRite instrumented walkway while participants performed the 6-minute walk test (6MWT). | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Step Length, Participants With Unilateral Amputation | Step length (cm) was assessed with a 16-foot CIR GAITRite instrumented walkway while participants performed the 6-minute walk test (6MWT). Step length is reported for both the prosthetic and sound (intact) limbs. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Step Length, Participants With Bilateral Amputation | Step length (cm) was assessed with a 16-foot CIR GAITRite instrumented walkway while participants performed the 6-minute walk test (6MWT). Step length is reported for both the prosthetic and sound (intact) limbs. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Step Time, Participants With Unilateral Amputation | Step time was assessed with a 16-foot CIR GAITRite instrumented walkway while participants performed the 6-minute walk test (6MWT). Step time is reported for both the prosthetic and sound (intact) limbs. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Step Time, Participants With Bilateral Amputation | Step time was assessed with a 16-foot CIR GAITRite instrumented walkway while participants performed the 6-minute walk test (6MWT). Step time is reported for both the prosthetic and sound (intact) limbs. | Participants were tested after using each foot in their prosthesis for 1 month. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Daily Step Activity, Participants With Unilateral Amputation | Daily step activity (steps / day) were measured over the 2-week period prior to assessment using a Orthocare Innovations Stepwatch 3 activity monitor. | Participants' step count data from the 2 weeks prior to in-person testing. | 
| Daily Step Activity, Participants With Bilateral Amputation | Daily step activity (steps / day) were measured over the 2-week period prior to assessment using a Orthocare Innovations Stepwatch 3 activity monitor. | Participants' step count data from the 2 weeks prior to in-person testing. | 
| Prosthetic Limb Users Survey of Mobility (PLUS-M), Participants With Unilateral Amputation | The PLUS-M is a self-report instrument designed to evaluate respondent's prosthetic mobility. It is scored using a standardized T-score centered on a national sample of unilateral lower limb prosthesis users (mean = 50, standard deviation = 10). Participants were administered the PLUS-M computerized adaptive test and 12-item form on an iPad tablet. The most precise score (i.e., score with the lowest error) was used for analysis. Absolute score range from 0 to 100. Higher T-scores indicate greater mobility. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Prosthetic Limb Users Survey of Mobility (PLUS-M), Participants With Bilateral Amputation | The PLUS-M is a self-report instrument designed to evaluate respondent's prosthetic mobility. It is scored using a standardized T-score centered on a national sample of unilateral lower limb prosthesis users (mean = 50, standard deviation = 10). Participants were administered the PLUS-M computerized adaptive test and 12-item form on an iPad tablet. The most precise score (i.e., score with the lowest error) was used for analysis. Absolute score range from 0 to 100. Higher T-scores indicate greater mobility. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Patient Reported Outcome Measurement Information System - Fatigue (PROMIS-Fatigue), Participants With Unilateral Amputation | The PROMIS-Fatigue is a self-report instrument designed to evaluate respondent's symptoms and effects of fatigue. It is scored using a standardized T-score centered on the US general population (mean = 50, standard deviation = 10). Participants were administered the computerized adaptive test and a 12-item short form on an iPad tablet. The most precise score (i.e., score with the lowest error) was used for analysis. Absolute score range from 0 to 100. Higher T-scores indicate greater fatigue. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Patient Reported Outcome Measurement Information System - Fatigue (PROMIS-Fatigue), Participants With Bilateral Amputation | The PROMIS-Fatigue is a self-report instrument designed to evaluate respondent's symptoms and effects of fatigue. It is scored using a standardized T-score centered on the US general population (mean = 50, standard deviation = 10). Participants were administered the computerized adaptive test and a 12-item short form on an iPad tablet. The most precise score (i.e., score with the lowest error) was used for analysis. Absolute score range from 0 to 100. Higher T-scores indicate greater fatigue. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Activities-Specific Balance Confidence Scale (ABC), Participants With Unilateral Amputation | The ABC is a self-report instrument designed to evaluate respondent's confidence in performing normal daily activities. It is scored from 0 to 4. Participants were administered an electronic version of the ABC on an iPad tablet. Scores range from 0 to 4. Higher scores indicate greater balance confidence. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Activities-Specific Balance Confidence Scale (ABC), Participants With Bilateral Amputation | The ABC is a self-report instrument designed to evaluate respondent's confidence in performing normal daily activities. It is scored from 0 to 4. Participants were administered an electronic version of the ABC on an iPad tablet. Scores range from 0 to 4. Higher scores indicate greater balance confidence. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Trinity Amputation Prosthesis Experience Scales, Revised (TAPES-R), Participants With Unilateral Amputation | The TAPES-R is a self-report instrument designed to evaluate respondent's activity restrictions and satisfaction with a prosthesis. The TAPES-R has three subscales (activity restrictions [TAPES-AR], functional satisfaction [TAPES-FUN], and aesthetic satisfaction [TAPES-AES], each scored from 0 to 2. Higher scores indicate more activity restrictions (TAPES-AR) or greater satisfaction (TAPES-FUN and TAPES-AES). Participants were administered an electronic version of the TAPES-R on an iPad tablet. | Participants were tested after using each foot in their prosthesis for 1 month. | 
| Trinity Amputation Prosthesis Experience Scales, Revised (TAPES-R), Participants With Bilateral Amputation | The TAPES-R is a self-report instrument designed to evaluate respondent's activity restrictions and satisfaction with a prosthesis. The TAPES-R has three subscales (activity restrictions [TAPES-AR], functional satisfaction [TAPES-FUN], and aesthetic satisfaction [TAPES-AES], each scored from 0 to 2. Higher scores indicate more activity restrictions (TAPES-AR) or greater satisfaction (TAPES-FUN and TAPES-AES). Participants were administered an electronic version of the TAPES-R on an iPad tablet. | Participants were tested after using each foot in their prosthesis for 1 month. |