Transfemoral Socket Design and Muscle Function

Summary

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.

Conditions

• Amputation

Interventions

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).

Sponsors & Collaborators

• Northwestern University

  collaborator OTHER

• University of Illinois at Chicago

  lead OTHER

Study Design

Allocation

NA

Purpose

TREATMENT

Masking

NONE

Model

SINGLE_GROUP

Eligibility

Min Age

21 Years

Max Age

85 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2019-09-24

Primary Completion

2022-09-23

Completion

2023-08-14

FDA Device

Yes

Countries

• United States

Study Locations