Metabolic Cost Savings for Transtibial Amputees Wearing the Controlled Energy Storage and Return (CESR) Foot

Study Overview
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Brief Summary
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To determine if below-knee amputees will walk with better efficiency wearing a CESR foot which stores energy at heel strike and releases energy releases energy during push-off.

Detailed Description
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Amputees work harder and have greater oxygen cost during ambulation compared to those without limb loss. Therefore, amputees generally walk slower and tire more easily than intact individuals. The loss of the ankle as a propulsive and supportive joint requires the amputee to perform extra muscular work with the hip, trunk and contralateral limb during ambulation. This increased muscular activity consumes additional metabolic energy and means that amputees have to work harder to walk at the same speed as intact individuals. For some amputees, this extra effort is simply not possible, and their loss of functional ambulation leads to a progressive spiral of disuse, reduced capacity and more disuse. Conversely, greater mobility can lead to greater activity and even more successful return to the workplace. The health consequences for amputees who do not maintain functional ambulation is multifactorial and costly, not only in terms of dollars for the institutions committed to their care, but also for the individuals themselves in terms of decreased quality of life, increased disability and pain. Recent developments have resulted in the design of a novel prosthetic foot that uses the energy from compressive forces during heel contact, stores it throughout midstance and releases it at an optimal instant during push-off in late stance. This unique design, with Controlled Energy Storage and Release (CESR) developed by a team at the University of Michigan, Ann Arbor has been shown to reduce the metabolic cost penalty of prosthetic ambulation (i.e. the increased cost over normal walking) by 50% compared to a standard SACH foot, but as yet only intact individuals wearing an aircast boot equipped with the prosthetic feet have been studied. It is likely that the increased energy savings will also be observed in transtibial amputees. Young, active amputees will soon be entering the VA system following operations in Iraq and Afghanistan, and the energy improvements may benefit this new VA patient population. The CESR foot may also provide substantial metabolic cost savings to older less active amputees currently in the VA system. By improving gait efficiency amputees will be better able to keep up with the demands of functional ambulation, remain more active and postpone many of the debilitating consequences of limited mobility. Therefore we propose to first refine the design of the CESR foot focusing on the energy storage and energy release mechanisms of the CESR foot. Several spring characteristics may prove optimal for certain subjects depending upon weight and walking characteristics. This will be an iterative optimization process with power generation and absorption characteristics of the CESR foot evaluated using computerized gait analysis and the lessons used for further refinement. The second phase will involve a three week wear-testing trial to determine if any improvement in gait economy, reduction in fatigue, improvement in comfort, or increase in the amount of daily walking can be achieved. A validated questionnaire will be utilized to determine each amputee's comfort and fatigue during a three week trial in their conventional foot and with the CESR foot. Step counts will be performed on each individual over the entire 3 week period with both the conventional foot and with the CESR foot. We will collect full body gait kinematics (motion) and kinetics (forces) using our Vicon 612 system, and metabolic measurements using our VmaxST to calculate oxygen cost for 24 transtibial amputees while walking with the CESR foot and their conventional foot. This will permit the calculation of the energy storage and release of the foot by inverse dynamics and calculate the net effect upon metabolic energy cost savings during ambulation at several speeds. If the CESR foot is successful in amputee gait these domains, our next step will be to perform a multi-center study with other VA motion laboratories, and eventually collaborate with Ohio Willow Wood, a prominent prosthetic manufacturer who has expressed an interest in bringing the CESR foot to market.

Official Title
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Metabolic Cost Savings for Transtibial Amputees Walking With the CESR Foot

Conditions
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Transtibial Amputation

Intervention / Treatment
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* Device: CESR Prosthetic Foot
* Device: typical prosthetic foot
* Device: standardized prosthetic foot


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Transtibial Amputees > 1 year walking with prosthesis Non-amputee control subjects Exclusion Criteria: Additional musculoskeletal pathology Cognitive limitation

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

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 |
| --- | --- |
| Active Comparator: Conventional Prosthetic foot<br>A conventional prosthetic foot that has limited energy storage and return capabilities. It is standardized and used by all subjects in the study. | Device: typical prosthetic foot<br>* patients will wear the prosthetic foot that they were prescribed by the care providers in the clinical team<br>|
| Active Comparator: Prescribed Prosthetic foot<br>the Prosthetic foot that the subject had prescribed for them by their clinical providers and was worn prior to study initiation | Device: standardized prosthetic foot<br>* a standard foot that has had weights applied to match the mass of the CESR foot<br>|
| Experimental: CESR foot<br>the experimental CESR, controlled energy storage prosthetic foot | Device: CESR Prosthetic Foot<br>* a novel prosthetic foot that is designed to store energy and release it at a predetermined time in the gait cycle<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Metabolic Oxygen Consumption During Ambulation | VO2 was collected at rest and while walking at a controlled walking speed of 1.14 meters/second for 10 minutes until they reached a steady state for 3 minutes. This was repeated for each foot condition. VO2 at the steady state was recorded in ml/min and were subsequently converted to calories and and then to Watts. The data were then corrected for body weight by dividing by weight in Kg. The gross VO2 in Watts/Kg during walking were then adjusted to net VO2 in Watts/kg by subtracting the resting metabolic rate. | Subjects were oriented to the testing protocol and each prosthetic foot on average 5 days prior to data collection and a acclimatization period of 5-10 minutes with each prosthetic foot prior to data collection | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Prosthetic Foot Push Off Peak Power | The biomechanical measurement of the power generated by the prosthetic foot during the push off component of stance phase. The peak power output during the push off component of stance phase was calculated in Joules. It was subsequently standardized for body weight in Kgs. The final units were therefore Joules/Kg. | Subjects were oriented to the testing protocol and each prosthetic foot on average 5 days prior to data collection and a acclimatization period of 5-10 minutes with each prosthetic foot prior to data collection | 
| Peak Intact Knee Loading | The biomechanical measure of the first peak of the knee external adduction moment | Subjects were oriented to the testing protocol and each prosthetic foot on average 5 days prior to data collection and a acclimatization period of 5-10 minutes with each prosthetic foot prior to data collection | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Amputee, Economy, Efficiency, Foot, Gait, Kinematics, Kinetics, Prosthesis