Transfemoral Socket Design and Muscle Function

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

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.

Study Overview

• Status: Completed
• Conditions: Amputation
• Intervention / Treatment: Device: Northwestern University Flexible Sub-Ischial Suction Socket (NU-FlexSIS)

• Study Type: Interventional
• Enrollment (Actual): 5
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Illinois
    • Chicago, Illinois, United States, 60612
      • University of Illinois at Chicago

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 21 years to 85 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

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).

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Baseline ischial containment to subischial socket

Device: Northwestern University Flexible Sub-Ischial Suction Socket (NU-FlexSIS); 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).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Residual Limb Hip Muscle Peak Torque 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) across the first three repetitions of 12.	Baseline
Residual Limb Hip Muscle Peak Torque 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) across the first three repetitions of 12. Comparison will be made to baseline measure.	8 weeks after intervention
Residual Limb Hip Muscle Peak Torque 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) across the first three repetitions of 12. Comparison will be made to baseline measure.	42 weeks after intervention
Residual Limb 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
Residual Limb 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
Residual Limb 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
Residual Limb Hip Muscle Duration at Baseline	Electromyographic (EMG) signals were recorded from transfemoral prosthesis users' residual limb muscles while walking. The duration of time each hip muscle was active during a stride was calculated as the percentage of the gait cycle (i.e., heel-strike to heel-strike) for which that EMG signal was above a baseline value (min: 0%, max: 100%). The larger the percentage of the gait cycle that a muscle was deemed to be active, the greater its duration.	Baseline
Residual Limb Hip Muscle Duration at 8-weeks	Electromyographic (EMG) signals were recorded from transfemoral prosthesis users' residual limb muscles while walking. The duration of time each hip muscle was active during a stride was calculated as the percentage of the gait cycle (i.e., heel-strike to heel-strike) for which that EMG signal was above a baseline value (min: 0%, max: 100%). The larger the percentage of the gait cycle that a muscle was deemed to be active, the greater its duration.	8 weeks after intervention
Residual Limb Hip Muscle Duration at at 42-weeks	Electromyographic (EMG) signals were recorded from transfemoral prosthesis users' residual limb muscles while walking. The duration of time each hip muscle was active during a stride was calculated as the percentage of the gait cycle (i.e., heel-strike to heel-strike) for which that EMG signal was above a baseline value (min: 0%, max: 100%). The larger the percentage of the gait cycle that a muscle was deemed to be active, the greater its duration.	42 weeks
Residual Limb Hip Muscle Integrated Area at Baseline	Electromyographic (EMG) signals were recorded from transfemoral prosthesis users' residual limb muscles while walking. The total amount of hip muscle activity was calculated as the integrated area under the EMG signal during a gait cycle (i.e., heel-strike to heel-strike). Each EMG signal was normalized (i.e., divided by its maximum value across all the gait cycles and multiple by 100. The integrated areas is therefore reported as a percentage of that maximum (min: 0%, max: 100%). The larger the integrated area the more the muscle was deemed to be active.	Baseline
Residual Limb Hip Muscle Integrated Area at 8-weeks	Electromyographic (EMG) signals were recorded from transfemoral prosthesis users' residual limb muscles while walking. The total amount of hip muscle activity was calculated as the integrated area under the EMG signal during a gait cycle (i.e., heel-strike to heel-strike). Each EMG signal was normalized (i.e., divided by its maximum value across all the gait cycles and multiple by 100. The integrated areas is therefore reported as a percentage of that maximum (min: 0%, max: 100%). The larger the integrated area the more the muscle was deemed to be active.	8 weeks after intervention
Residual Limb Hip Muscle Integrated Area at 42-weeks	Electromyographic (EMG) signals were recorded from transfemoral prosthesis users' residual limb muscles while walking. The total amount of hip muscle activity was calculated as the integrated area under the EMG signal during a gait cycle (i.e., heel-strike to heel-strike). Each EMG signal was normalized (i.e., divided by its maximum value across all the gait cycles and multiple by 100. The integrated areas is therefore reported as a percentage of that maximum (min: 0%, max: 100%). The larger the integrated area the more the muscle was deemed to be active.	42 weeks after intervention
Peak Residual Limb Hip Muscle Activity at Baseline	Electromyographic (EMG) signals were recorded from transfemoral prosthesis users' residual limb muscles while walking. The highest level of hip muscle activity was calculated as the peak of the EMG signal during a gait cycle (i.e., heel-strike to heel-strike). Each EMG signal was normalized (i.e., divided by its maximum value across all the gait cycles recorded during baseline). The peak EMG is therefore typically reported as a value between 0 and 1. However, if the peak value during assessments increases relative to baseline, the value of the peak activity will exceed 1. The larger the peak value the greater the activation of that muscle.	Baseline
Peak Residual Limb Hip Muscle Activity at 8 Weeks	Electromyographic (EMG) signals were recorded from transfemoral prosthesis users' residual limb muscles while walking. The highest level of hip muscle activity was calculated as the peak of the EMG signal during a gait cycle (i.e., heel-strike to heel-strike). Each EMG signal was normalized (i.e., divided by its maximum value across all the gait cycles recorded during baseline). The peak EMG is therefore typically reported as a value between 0 and 1. However, if the peak value during assessments increases relative to baseline, the value of the peak activity will exceed 1. The larger the peak value the greater the activation of that muscle.	8 weeks after intervention
Peak Residual Limb Hip Muscle Activity at 42 Weeks	Electromyographic (EMG) signals were recorded from transfemoral prosthesis users' residual limb muscles while walking. The highest level of hip muscle activity was calculated as the peak of the EMG signal during a gait cycle (i.e., heel-strike to heel-strike). Each EMG signal was normalized (i.e., divided by its maximum value across all the gait cycles recorded during baseline). The peak EMG is therefore typically reported as a value between 0 and 1. However, if the peak value during assessments increases relative to baseline, the value of the peak activity will exceed 1. The larger the peak value the greater the activation of that muscle.	42 weeks after intervention

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Four Square Step Test at Baseline	A test of dynamic balance and coordination that assesses the participant's ability to step over objects forward, sideways, and backwards. Test was administered and scored as the best time (i.e., fastest) of two trials.	Baseline
Four Square Step Test at 8 Weeks	A test of dynamic balance and coordination that assesses the participant's ability to step over objects forward, sideways, and backwards. Test was administered and scored as the best time (i.e., fastest) of two trials.	8-weeks after intervention
Four Square Step Test at 42 Weeks	A test of dynamic balance and coordination that assesses the participant's ability to step over objects forward, sideways, and backwards. Test was administered and scored as the best time (i.e., fastest) of two trials.	42-weeks after intervention
One Leg Stance Test at Baseline	A test of static balance that assesses the participant's ability to remain upright on one leg. Test was administered and scored as the best time (i.e., longest) of two trials. Longer times imply better static balance.	Baseline
One Leg Stance Test at 8 Weeks	A test of static balance that assesses the participant's ability to remain upright on one leg. Test was administered and scored as the best time (i.e., longest) of two trials. Longer times imply better static balance.	8 weeks after intervention
One Leg Stance Test at 42 Weeks	A test of static balance that assesses the participant's ability to remain upright on one leg. Test was administered and scored as the best time (i.e., longest) of two trials. Longer times imply better static balance.	42 weeks after intervention
10-Meter Walk Test at Baseline	The 10MWT assesses walking speed in meters per second over a short duration. A faster speed is consider better walking performance. The fastest of 2 trials was used.	Baseline
10-Meter Walk Test at 8 Weeks	The 10MWT assesses walking speed in meters per second over a short duration. A faster speed is consider better walking performance. The fastest of 2 trials was used.	8 weeks after intervention
10-Meter Walk Test at 42 Weeks	The 10MWT assesses walking speed in meters per second over a short duration. A faster speed is consider better walking performance. The fastest of 2 trials was used.	42 weeks after intervention
2-Minute Walk Test at Baseline	The 2-Minute Walk Test is a measurement of waking endurance that assesses walking distance over two minutes. A longer distance walked indicates greater walking endurance.	Baseline
2-Minute Walk Test at 8 Weeks	The 2-Minute Walk Test is a measurement of waking endurance that assesses walking distance over two minutes. A longer distance walked indicates greater walking endurance.	8-weeks after intervention.
2-Minute Walk Test at 42 Weeks	The 2-Minute Walk Test is a measurement of waking endurance that assesses walking distance over two minutes. A longer distance walked indicates greater walking endurance.	42-weeks after intervention.
Volume of Physical Activity at Baseline	To assess the volume of physical activity, transfemoral prosthesis users wore a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for a 2-week period. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from the 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)
Volume of Physical Activity at 8 Weeks	To assess the volume of physical activity, transfemoral prosthesis users wore a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for a 2-week period. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from the 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.	8-weeks after intervention
Volume of Physical Activity at 42 Weeks	To assess the volume of physical activity, transfemoral prosthesis users wore a StepWatch4 activity monitor (Modus Health, Edmonds, WA) for a 2-week period. Activity bouts, or periods of time in which steps occur in successive 10-second intervals, will be derived from the 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.	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 a 2-week period. 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)
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 a 2-week period. 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.	8 weeks after intervention
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 a 2-week period. 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.	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 a 2-week period. 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 a 2-week period. 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.	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 a 2-week period. 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.	42 weeks after intervention

Collaborators and Investigators

• Sponsor: University of Illinois at Chicago
• Collaborators: Northwestern University

Study record dates

Study Major Dates

• Study Start (Actual): September 24, 2019
• Primary Completion (Actual): September 23, 2022
• Study Completion (Actual): August 14, 2023

Study Registration Dates

• First Submitted: December 20, 2019
• First Submitted That Met QC Criteria: December 23, 2019
• First Posted (Actual): December 26, 2019

Study Record Updates

• Last Update Posted (Actual): October 10, 2024
• Last Update Submitted That Met QC Criteria: September 17, 2024
• Last Verified: September 1, 2024

More Information

Terms related to this study

• Other Study ID Numbers: 2019-0725; W81XWH1910507 (Other Grant/Funding Number: Department of Defense)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: No