Comparative Performance of Dynamic Elastic Response Feet

Study Overview
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Brief Summary
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The purpose of this study was to compare the functional performance of individuals with transtibial amputation using two types of prosthetic foot designs: carbon fiber vs. fiberglass composite.

Detailed Description
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Recently, a new type of prosthetic foot has appeared on the market. This device is composed of a fiberglass composite material. Knowledge is lacking regarding the performance characteristics of this new device. Comprehensive studies are needed to form a solid basis for prosthetic prescription. The current study sought to understand the experience of community-living, transtibial amputees using this prosthetic foot. Specifically, the biomechanical performance of this device were compared to existing conventional dynamic elastic response (DER) technology in a controlled laboratory setting. The investigators hypothesized that the fiberglass composite material provided more energy return and improved ankle kinematics performance. The study design was a repeated measures cross-over trial whereby only the prosthetic foot was changed. Each subject was tested using their current carbon-fiber energy storage and return prosthetic foot (CFPF) and the fiberglass composite energy storage and return prosthetic foot (Rush, Ability Dynamics) (FPF). Half of the subjects began the study on the CFPF while the other half began on the FPF. All types of CFPF were used in this study. Each subject was given an acclimation period (about 4 weeks) before testing, which was consistent with other similar studies. The same socket and suspension were used throughout the study in order to eliminate these confounding variables. A 10 camera, high resolution motion capture system with a set of 51 reflective markers was used to capture whole-body motion. Three-dimensional marker trajectory data was collected at 120 Hz and filtered using a fourth-order Butterworth low-pass filter with a cutoff frequency of 8 Hz. The standard Helen Hayes marker set and some additional markers were applied to the subject. Additional markers included an anterior pylon marker, medial pylon marker, lateral pylon marker, right and left medial calcaneus markers, and right and left lateral calcaneus markers. In addition, left and right medial knee markers were used for establishing the knee joint centers and were then removed for the walking trails. Subjects wore standard laboratory athletic shoes for all walking trials. All of the markers associated with the foot were placed on the outside of the subject's shoes. Following the application of the reflective marker set, the subject performed tests while walking over level ground at a self-selected and normalized speed as well as up and down a 10 degree inclined ramp. The normalized speed controlled for leg length by normalizing to a Froude (Fr) number of 0.25 where Fr = v^2/gl, and v is the walking speed, g is the gravitational constant, and l is the leg length using the greater trochanter height as leg length. Timing gates were used to control the walking speed. Simultaneously, ground reaction force data was collected from force plates at a sampling rate of 600 Hz. Data from these force plates was time-synchronized with the motion cameras. The ramp had a force plate embedded within the ramp.

Official Title
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Comparative Performance of Dynamic Elastic Response Feet

Conditions
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Transtibial Amputation - Unilateral

Intervention / Treatment
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* Device: Fiberglass Composite foot
* Device: Carbon Fiber Composite Foot


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Unilateral transtibial amputee Currently using a carbon fiber prosthetic (DER) foot for at least the last 6 months Stable stump volume over the past 6 months Medicare Functional Classification Level K3 or K4 Exclusion Criteria: Neuromuscular problems such as previous stroke or contralateral amputation Use of gait aids for ambulation Undergoing dialysis Poor prosthetic socket fit or stump problems (e.g., skin breakdown)

Ages Eligible for Study
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Minimum Age: 21 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: Non-Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: This was a repeated measures cross-over trial whereby only the prosthetic foot was changed. Each subject was tested using their current carbon-fiber prosthetic foot (CFPF), and the fiberglass prosthetic foot (FPF). Half of the subjects began the study on the CFPF while the other half began on the FPF. Each subject was given an acclimation period of 4 weeks before testing.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: CFPF first, then FPF<br>After a 4 week acclimation period, subjects were studied on their current carbon fiber composite foot (CFPF), followed by another 4 week acclimation period, then studied on the study provided fiberglass composite foot (FPF). | Device: Fiberglass Composite foot<br>* The Rush foot is a fiberglass composite energy storage and return prosthetic foot.<br>* Other names: Rush Foot;Device: Carbon Fiber Composite Foot<br>* All types of currently commercially available carbon fiber energy storage and return prosthetic feet will be considered appropriate.<br>* Other names: Freedom Agilix;|
| Experimental: FPF first, then CFPF<br>After a 4 week acclimation period, subjects were studied on the study provided fiberglass composite foot (FPF), followed by another 4 week acclimation period, then studied on their current carbon fiber composite foot (CFPF). | Device: Fiberglass Composite foot<br>* The Rush foot is a fiberglass composite energy storage and return prosthetic foot.<br>* Other names: Rush Foot;Device: Carbon Fiber Composite Foot<br>* All types of currently commercially available carbon fiber energy storage and return prosthetic feet will be considered appropriate.<br>* Other names: Freedom Agilix;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Peak Ankle Dorsiflexion During Stance | The peak ankle dorsiflexion is the peak ankle backward flexion or bending when walking. | After approximate 4 week acclimation period | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Peak Ankle Plantar Flexor Moment During Stance | Peak ankle plantar flexor moment means the peak force of the movement of the foot in which the foot or toes flex downward toward the sole. The unit of measurement for this variable is Nm/kg = 1 nanometer / (kilogram unit). | After approximate 4 week acclimation period | 
| Peak Ankle Power Generation | Joint power (P) is the dot product of the moment (M) at the joint and the angular velocity (w) of the distal segment with respect to the proximal segment (i.e., P = M · w). Depending on the direction of the moment and the direction of the angular velocity, the power can be positive or negative. If the signs for the moment and angular velocity are both positive or both negative, the power is positive. If the signs for the moment and angular velocity are different, the power is negative. The unit of measurement for this variable is W/kg = watts/kilogram. | After approximate 4 week acclimation period | 
| Peak Knee Flexion During Swing | A gait cycle is the period of time for one stride, that is, the time from one event (usually initial foot contact) to the next occurrence of the same event with the same foot. For each leg, the gait cycle can be divided into a stance phase and a swing phase. This variable is measuring the angle of knee flexion during the swing phase. | After approximate 4 week acclimation period | 
| Time of Peak Knee Flexion During Swing | A gait cycle is the period of time for one stride, that is, the time from one event (usually initial foot contact) to the next occurrence of the same event with the same foot. For each leg, the gait cycle can be divided into a stance phase and a swing phase. This variable is expressed as a percentage of the gait cycle. | After approximate 4 week acclimation period | 
| Patient Satisfaction as Measured by the Prosthesis Evaluation Questionnaire (PEQ) | The PEQ is a self-administered questionnaire composed of nine scales computed from forty-two items (ambulation, appearance, frustration, perceived response, residual limb health, social burden, sounds, utility, well being). Each question uses a visual analog scale format, scored as a continuous numerical variable measured as the distance in millimeters from the left endpoint of the measured from the left (0-100). The 0 side of the scale is very negative (terrible) and the 100 side of the scale is very positive (excellent). Each scale is reported separately, with a higher score indicating more satisfaction with the prosthesis itself or quality of life. | After approximate 4 week acclimation period |