Transfemoral Socket Design and Muscle Function

Study Overview
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Brief Summary
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The objective of this pilot research project is to evaluate the effect of prosthetic socket design on amputated limb hip muscle strength and endurance in Service members, Veterans, and civilians who use above-the-knee prostheses. Traditional above-the-knee socket designs provide pelvic support that interferes with hip motion. They may also reduce the effort required from amputated limb hip muscles to stabilize the hip and amputated limb, risking further loss of muscle mass and strength beyond that due to amputation. Long-standing use of above-the-knee sockets with pelvic support may therefore intensify amputated limb muscle loss and weakness, leading to challenges with walking and balance, increasing the effort required to walk, and contributing to degenerative changes in the hips and knees. Alternative socket designs that lessen the loss of muscle mass and strength are therefore required. The investigators have developed a new socket without pelvic support for above-the-knee prosthesis users called the Northwestern University Flexible Sub-Ischial Suction (NU-FlexSIS) Socket. This new socket design increases user comfort and is often preferred by users over sockets with pelvic support. This new socket does not lessen the mechanical function of the socket, or walking and balance performance. Our recent research suggests that walking with this new socket may also increase amputated limb hip muscle size. However, more research is needed to demonstrate that this new socket design improves amputated limb hip muscle strength and endurance, leading to better function. A socket design that increases amputated limb hip muscle strength and endurance would provide a simple way to restore amputated limb hip muscle weakness in above-the-knee prosthesis users. Despite a considerable decrease in hip muscle size and strength due to amputation surgery, amputated limb hip muscles are expected to compensate for the loss of knee and ankle function by providing stability and propulsion during walking. Walking in the new socket design without pelvic support is expected to increase amputated limb hip muscle strength and endurance, providing an appealing alternative to traditional resistance training in order to retain hip muscle strength. Unlike traditional resistance training, using this new socket design would not require additional time or equipment, and may be effective just by walking in the home, community, or workplace. Due to existing infrastructure (e.g., ongoing clinical adoption of the NU-FlexSIS Socket, existing instructional materials and courses for fabrication and fitting of the NU-FlexSIS Socket, as well as a continuing partnership with Chicago's largest provider of prosthetic clinical care), the investigators anticipate being able to translate our research results to clinical practice by the end of the project period. The investigators expect the results of the proposed pilot research project to directly and positively benefit the health and well-being of Service members, Veterans, and civilians who are above-the-knee prosthesis users. Benefits of increasing amputated limb hip muscle strength and endurance may include: i) improved control over the prosthesis, ii) better balance, iii) reduced effort to walk, and iv) protection against joint degeneration. For Service members these benefits could improve their performance on challenging and/or uneven ground, and increase the distance and speed they can walk or run. For Veterans, these benefits could lead to greater independence during activities of daily living, and fewer falls, reducing the physical and emotional burden on family members and caregivers.

Official Title
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A Pilot Clinical Trial to Assess the Effect of Transfemoral Socket Design on Hip Muscle Function

Conditions
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Amputation

Intervention / Treatment
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* Device: Northwestern University Flexible Sub-Ischial Suction Socket (NU-FlexSIS)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: worn an ischial containment socket for ≥ 2 years, able to walk short distances (10 meters), ability to read, write, and speak English, ≥ 2 years using a liner-based suspension, and a residual limb length ≥ 5. Exclusion Criteria: amputation of a second leg, contralateral complications (e.g., hip replacement), or other major neuromusculoskeletal or cardiovascular conditions (e.g., heart failure).

Ages Eligible for Study
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Minimum Age: 21 Years
Maximum Age: 85 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
Intervention Model: Single Group Assignment
Interventional Model Description: Transfemoral amputees who historically have worn an ischial containment prosthetic socket will be assessed at baseline, fit with the intervention (a sub-ischial socket), and then tested at 8 and 42 weeks after intervention. All comparisons will be made back to baseline.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Baseline ischial containment to subischial socket<br> | Device: Northwestern University Flexible Sub-Ischial Suction Socket (NU-FlexSIS)<br>* The sub-ischial socket includes a firm, compressive, preferably cylindrical, fabric-covered silicone liner, a flexible inner socket, and a shorter rigid outer socket. The socket has proximal trim lines that do not impinge on the pelvis; they terminate distal to the ischial tuberosity and greater trochanter. For the NU-FlexSIS Socket, passive suction suspension is achieved using a one way valve and a liner with an internal seal. Since the prosthetic socket is a custom-made device, it is considered Class I exempt by the Food and Drug Administration (FDA).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Hip muscle strength at baseline | Hip flexor, extensor, adductor and abductor muscle strength will be measured in transfemoral prosthesis users using a motor-driven isokinetic dynamometer. Muscular strength will be assessed via average peak torque (i.e., highest torque) and rate of torque development (i.e., slope of the torque/time curve from onset to peak) across the first three repetitions of 12. | Baseline | 
| Change in hip muscle strength at 8-weeks | Hip flexor, extensor, adductor and abductor muscle strength will be measured in transfemoral prosthesis users using a motor-driven isokinetic dynamometer. Muscular strength will be assessed via average peak torque (i.e., highest torque) and rate of torque development (i.e., slope of the torque/time curve from onset to peak) across the first three repetitions of 12. Comparison will be made to baseline measure. | 8 weeks after intervention | 
| Change in hip muscle strength at 42-weeks | Hip flexor, extensor, adductor and abductor muscle strength will be measured in transfemoral prosthesis users using a motor-driven isokinetic dynamometer. Muscular strength will be assessed via average peak torque (i.e., highest torque) and rate of torque development (i.e., slope of the torque/time curve from onset to peak) across the first three repetitions of 12. Comparison will be made to baseline measure. | 42 weeks after intervention | 
| Hip muscle endurance at baseline | Hip flexor, extensor, adductor and abductor muscle endurance will be measured in transfemoral prosthesis users using a motor-driven isokinetic dynamometer. Muscular endurance will be assessed via a fatigue index, calculated as a percentage of the difference between total work performed during the first and last 3 repetitions divided by total work over the first 3 repetitions. A higher fatigue index will be taken as evidence of reduced muscular endurance. | Baseline | 
| Change in hip muscle endurance at 8-weeks | Hip flexor, extensor, adductor and abductor muscle endurance will be measured in transfemoral prosthesis users using a motor-driven isokinetic dynamometer. Muscular endurance will be assessed via a fatigue index, calculated as a percentage of the difference between total work performed during the first and last 3 repetitions divided by total work over the first 3 repetitions. A higher fatigue index will be taken as evidence of reduced muscular endurance. Comparison will be made to baseline measure. | 8 weeks after intervention | 
| Change in hip muscle endurance at 42-weeks | Hip flexor, extensor, adductor and abductor muscle endurance will be measured in transfemoral prosthesis users using a motor-driven isokinetic dynamometer. Muscular endurance will be assessed via a fatigue index, calculated as a percentage of the difference between total work performed during the first and last 3 repetitions divided by total work over the first 3 repetitions. A higher fatigue index will be taken as evidence of reduced muscular endurance. Comparison will be made to baseline measure. | 42 weeks after intervention | 
| Hip muscle onset and offset times at baseline | The onset and offset times of residual limb hip muscles will be calculated from electromyographic signals recorded while walking using surface electrodes. | Baseline | 
| Changes in hip muscle onset and offset times at 8-weeks | The onset and offset times of residual limb hip muscles will be calculated from electromyographic signals recorded while walking using surface electrodes. Comparison will be made to baseline measure. | 8 weeks after intervention | 
| Changes in hip muscle onset and offset times at 42-weeks | The onset and offset times of residual limb hip muscles will be calculated from electromyographic signals recorded while walking using surface electrodes. Comparison will be made to baseline measure. | 42 | 
| Hip muscle integrated area at baseline | The integrated area of electromyographic signals will be calculated from residual limb hip muscles recorded using surface electrodes while walking. | Baseline | 
| Change in hip muscle integrated area at 8-weeks | The integrated area of electromyographic signals will be calculated from residual limb hip muscles recorded using surface electrodes while walking. Comparison will be made to baseline measure. | 8 weeks after intervention | 
| Change in hip muscle integrated area at 42-weeks | The integrated area of electromyographic signals will be calculated from residual limb hip muscles recorded using surface electrodes while walking. Comparison will be made to baseline measure. | 42 weeks after intervention | 
| Peak hip muscle activity at baseline | The peak activity of residual limb hip muscles will be characterized from electromyographic signals recorded while walking using surface electrodes. | Baseline | 
| Peak hip muscle activity at 8 weeks | The peak activity of residual limb hip muscles will be characterized from electromyographic signals recorded while walking using surface electrodes. Comparison will be made to baseline measure. | 8 weeks after intervention | 
| Peak hip muscle activity at 42 weeks | The peak activity of residual limb hip muscles will be characterized from electromyographic signals recorded while walking using surface electrodes. Comparison will be made to baseline measure. | 42 weeks after intervention | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Four Square Step Test (dynamic balance) at baseline | Four Square Step Test (dynamic balance) will be administered and scored as the best time (i.e., fastest) of two trials. | Baseline | 
| Change in Four Square Step Test (dynamic balance) at 8 weeks | Four Square Step Test (dynamic balance) will be administered and scored as the best time (i.e., fastest) of two trials. Comparisons will be made to baseline. | 8-weeks after intervention | 
| Change in Four Square Step Test (dynamic balance) at 42 weeks | Four Square Step Test (dynamic balance) will be administered and scored as the best time (i.e., fastest) of two trials. Comparisons will be made to baseline. | 42-weeks after intervention | 
| One Leg Stance Test (static balance) at baseline | One Leg Stance Test (static balance) will be administered and scored as the best time (i.e., longest) of two trials. | Baseline | 
| One Leg Stance Test (static balance) at 8 weeks | One Leg Stance Test (static balance) will be administered and scored as the best time (i.e., longest) of two trials. Comparisons will be made to baseline. | 8 weeks after intervention | 
| One Leg Stance Test (static balance) at 42 weeks | One Leg Stance Test (static balance) will be administered and scored as the best time (i.e., longest) of two trials. Comparisons will be made to baseline. | 42 weeks after intervention | 
| 10-Meter Walk Test (walking speed) at baseline | One Leg Stance Test (static balance) will be administered and scored as the best time (i.e., fastest time) of two trials. | Baseline | 
| Change in 10-Meter Walk Test (walking speed) at 8 weeks | One Leg Stance Test (static balance) will be administered and scored as the best time (i.e., fastest time) of two trials. Comparisons will be made to baseline. | 8 weeks after intervention | 
| Change in 10-Meter Walk Test (walking speed) at 42 weeks | One Leg Stance Test (static balance) will be administered and scored as the best time (i.e., fastest time) of two trials.Comparisons will be made to baseline. | 42 weeks after intervention | 
| 2-Minute Walk Test (walking endurance) at baseline | 2-Minute Walk Test (walking endurance) will be administered and scored as the distance walked in 2 minutes. | Baseline | 
| Change in 2-Minute Walk Test (walking endurance) at 8 weeks | 2-Minute Walk Test (walking endurance) will be administered and scored as the distance walked in 2 minutes. Comparisons will be made to baseline. | 8-weeks after intervention. | 
| Change in 2-Minute Walk Test (walking endurance) at 42 weeks | 2-Minute Walk Test (walking endurance) will be administered and scored as the distance walked in 2 minutes. Comparisons will be made to baseline. | 42-weeks after intervention. | 
| Volume of physical activity at baseline | To assess the volume of physical activity, transfemoral prosthesis users will wear a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for three 2-week periods. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from step count data. The volume of physical activity will be quantified by the mean number of steps per activity bout.Higher values will be taken as evidence of greater physical activity. | 2 weeks prior to intervention (baseline) | 
| Change in volume of physical activity at 8 weeks | To assess the volume of physical activity, transfemoral prosthesis users will wear a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for three 2-week periods. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from step count data. The volume of physical activity will be quantified by the mean number of steps per activity bout.Higher values will be taken as evidence of greater physical activity. Comparisons will be made to baseline. | 8-weeks after intervention | 
| Change in volume of physical activity at 42 weeks | To assess the volume of physical activity, transfemoral prosthesis users will wear a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for three 2-week periods. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from step count data. The volume of physical activity will be quantified by the mean number of steps per activity bout. Higher values will be taken as evidence of greater physical activity. Comparisons will be made to baseline. | 42-weeks after intervention | 
| Frequency of physical activity at baseline | To assess the frequency of physical activity, transfemoral prosthesis users will wear a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for three 2-week periods. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from step count data. The frequency of physical activity will be quantified by the mean number of activity bouts per day. Higher values will be taken as evidence of greater physical activity. | 2 weeks prior to intervention (baseline) | 
| Change in frequency of physical activity at 8 weeks | To assess the frequency of physical activity, transfemoral prosthesis users will wear a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for three 2-week periods. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from step count data. The frequency of physical activity will be quantified by the mean number of activity bouts per day. Higher values will be taken as evidence of greater physical activity. Comparisons will be made to baseline. | 8 weeks after intervention | 
| Change in frequency of physical activity at 42 weeks | To assess the frequency of physical activity, transfemoral prosthesis users will wear a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for three 2-week periods. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from step count data. The frequency of physical activity will be quantified by the mean number of activity bouts per day. Higher values will be taken as evidence of greater physical activity. Comparisons will be made to baseline. | 42 weeks after intervention | 
| Duration of physical activity at baseline | To assess the duration of physical activity, transfemoral prosthesis users will wear a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for three 2-week periods. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from step count data. The duration of physical activity will be quantified by the mean time (in minutes) of activity bouts per day. Higher values will be taken as evidence of greater physical activity. | 2 weeks prior to intervention (baseline) | 
| Duration of physical activity at 8 weeks | To assess the duration of physical activity, transfemoral prosthesis users will wear a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for three 2-week periods. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from step count data. The duration of physical activity will be quantified by the mean time (in minutes) of activity bouts per day. Higher values will be taken as evidence of greater physical activity. Comparisons will be made to baseline. | 8 weeks after intervention | 
| Duration of physical activity at 42 weeks | To assess the duration of physical activity, transfemoral prosthesis users will wear a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for three 2-week periods. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from step count data. The duration of physical activity will be quantified by the mean time (in minutes) of activity bouts per day. Higher values will be taken as evidence of greater physical activity. Comparisons will be made to baseline. | 42 weeks after intervention |