Sub-Ischial Socket for Transfemoral Amputation and Lower Mobility

December 9, 2025 updated by: Stefania Fatone, University of Washington

Evaluation of the Northwestern University Subischial Socket for Persons With Transfemoral Amputation and Lower Mobility Levels

The objective of this trial is to assess use and benefits of the subischial socket for persons with transfemoral amputation and lower mobility levels. Specifically, the investigators will evaluate whether the subischial socket improves comfort, socket wear time, mobility, participation, quality of life and satisfaction with device than the standard-of-care ischial containment socket.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

Prosthetic sockets that are currently used by persons with above-the-knee amputation (AKA) fit intimately with the thigh and pelvis, limiting hip motion and causing discomfort. Socket comfort while standing and sitting is of great importance to persons with lower limb amputation. Yet discomfort while sitting has been reported in 44% of persons with AKA. In those with AKA who are more sedentary, clinical observation indicates that socket discomfort in sitting results in less prosthesis wear time and less mobility with the prosthesis. Based on these observations, the investigators propose that improving socket comfort in persons with AKA who have lower mobility will increase the time spent wearing the socket, which will in turn increase mobility, and in turn again improve satisfaction with the prosthesis and overall quality-of-life. A new prosthetic socket design, the sub-ischial socket, which eliminates contact with the pelvis, has been developed with the intent of improving comfort and hip motion in people with AKA. In particular, sitting comfort has been highlighted as an advantage of this new socket design by early users. Therefore, the objective of this project is to assess use and benefits of the sub-ischial socket for persons with AKA and lower mobility levels. The investigators will evaluate whether the sub-ischial socket is more comfortable, improves prosthesis wear time, mobility, participation in society, satisfaction with device, skin-related quality-of-life, and health-related quality of life compared to the current standard-of-care socket design in persons with AKA and lower mobility levels. If a participant is eligible and enrolled into this study, participation would last about 10 months and would involve up to 8 in-person visits (for individuals receiving a new sub-ischial socket). Individuals receiving a new sub-ischial socket will also be asked to wear a step counter and temperature sensor and complete 11 remote survey assessments spread over the 10-month period of the study. Data will also be collected from a reference group of participants with transfemoral amputation and lower mobility levels who will not receive a sub-ischial socket. These participants will be assessed while wearing their clinically-provided, standard-of-care ischial containment socket. These participants will complete 8 remote survey assessments over a 10-month period.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
84

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.
  • Name: Rana Salem, MA
  • Phone Number: 206-221-2414
  • Email: rsalem@uw.edu

Study Contact Backup

  • Name: Stefania Fatone, PhD
  • Phone Number: 206-685-7918
  • Email: sfaton@uw.edu

Study Locations

  • United States
    • Minnesota
      • Minneapolis, Minnesota, United States, 55417
        • Minneapolis VA Health Care System
    • Texas
      • Houston, Texas, United States, 78758
        • Hanger Institute for Clinical Research and Education
    • Washington
      • Seattle, Washington, United States, 98195
        • University of Washington

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  1. Speak and read English;
  2. Provision of signed and dated informed consent form;
  3. Stated willingness to comply with all study procedures and availability for the duration of the study;
  4. All sexes and genders age 18 years and older;
  5. Have a unilateral transfemoral or knee disarticulation amputation and have used a prosthesis for 1 year or more;
  6. Be classified by their prosthetist as being a Medicare Functional Classification Level of K2 (limited community ambulator);
  7. Have never worn a sub-ischial socket;
  8. Current IC socket and prosthesis must be well fitting and maintained; current socket must have pelvic weightbearing and/or containment;
  9. Participant has no plans to change the knee or foot in the next 10 months;
  10. Willingness to adhere to the monitoring and new socket regimen;
  11. Have sufficient upper limb function to don liner and change sensors;
  12. Access to necessary resources for participating in the study (i.e., computer, smartphone, internet access, telephone):
  13. Be a Veteran (VA site only).

Exclusion Criteria (intervention group only):

  1. Have a femoral length <5 inches;
  2. Have a known silicone allergy;
  3. Are unable to don or tolerate wearing a compressive liner;
  4. Loss of metatarsal heads on contralateral limb;
  5. Active malignancy;
  6. Pregnancy;
  7. Polytrauma that affects functional ability beyond that of a unilateral transfemoral amputation.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Non-Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Intervention Group
Participants will be assessed for 12 weeks in their usual ischial containment socket before receiving a subischial socket to be worn and assessed for 24 weeks.
Device: Northwestern University Flexible Subischial Suction Socket (NU-FlexSIS)
A custom-made prosthetic socket for transfemoral amputation that consists of proximal trimlines that do not interact with the pelvis.
No Intervention: Reference Group
Participants will be assessed for 40 weeks in their usual ischial containment socket. No intervention will be provided.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Change in Socket Comfort Score (SCS)
Time Frame: Change from week 12 to week 24 compared between Intervention and Reference Groups.
Single item self-report measure to rate average socket comfort on an 11-point scale where 0 represents the most uncomfortable socket fit participant can imagine and 10 represents the most comfortable socket fit participant can imagine. Participants will rate their socket comfort in general, and while sitting, standing, and walking.
Change from week 12 to week 24 compared between Intervention and Reference Groups.

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Temperature sensor
Time Frame: Intervention group only: Baseline period weeks 0-12; Intervention period weeks 0-24.
Temperature sensor measures and records temperature and time at variable intervals. The temperature sensor will be retrofit to the liner worn with the usual socket and installed in the liner worn with the sub-ischial socket so that wear time can be monitored for the entire study duration.
Intervention group only: Baseline period weeks 0-12; Intervention period weeks 0-24.
Step counter
Time Frame: Intervention group only: Baseline period weeks 0-4; Intervention period weeks 0-4 and 20-24.
A step counter activity monitor is an ankle-worn, microprocessor-controlled, two-dimensional accelerometer that measures step counts and step rates per unit time.
Intervention group only: Baseline period weeks 0-4; Intervention period weeks 0-4 and 20-24.
Falls
Time Frame: All participants: Baseline period weeks 0, 4, 8, 12; Intervention group: Intervention period weeks 0, 4, 8, 12, 16, 20, 24; Reference group: Monitoring period weeks 4, 12, 20, 24.
Falls will be self-reported by participants at each assessment time point. Participants will be asked if they have fallen in the past 4 weeks. If the participant indicates that they have fallen, they will ask how many times they have fallen in the past 4 weeks, whether the fall resulted in an injury, and if applicable, type of injury and whether they sought medical attention for the fall.
All participants: Baseline period weeks 0, 4, 8, 12; Intervention group: Intervention period weeks 0, 4, 8, 12, 16, 20, 24; Reference group: Monitoring period weeks 4, 12, 20, 24.
Activities-specific Balance Confidence (ABC) Scale
Time Frame: All participants: Baseline period weeks 0, 4, 8, 12; Intervention group: Intervention period weeks 4, 8, 12, 16, 20, 24; Reference group: Monitoring period weeks 4, 12, 20, 24.
16-item self-report measure where individuals rate their balance confidence in performing various activities without losing balance or experiencing a sensation of unsteadiness. Items are rated on a scale from 0-4, with 0 representing no balance confidence and 4 representing complete balance confidence. Total scores are created by averaging across the 16 items, with total scores ranging from 0 to 4. The higher the total score, the better the balance confidence.
All participants: Baseline period weeks 0, 4, 8, 12; Intervention group: Intervention period weeks 4, 8, 12, 16, 20, 24; Reference group: Monitoring period weeks 4, 12, 20, 24.
Prosthesis Evaluation Questionnaire (PEQ) Residual Limb Health
Time Frame: All participants: Baseline period weeks 0, 4, 8, 12; Intervention group: Intervention period weeks 0, 4, 8, 12, 16, 20, 24; Reference group: Monitoring period weeks 4, 12, 20, 24.
6-item self-report measure where individuals rate severity of residual limb issues such as rashes, sores, or sweating. Items are rated on a scale from 0-10, with 0 indicating that a residual limb problem/issue is very bothersome and 10 indicating that it is not at all bothersome. Total score is created by averaging across the 6 items, with possible scores ranging from 0-10. The higher the total score, the better the residual limb health.
All participants: Baseline period weeks 0, 4, 8, 12; Intervention group: Intervention period weeks 0, 4, 8, 12, 16, 20, 24; Reference group: Monitoring period weeks 4, 12, 20, 24.
Roland-Morris Disability Questionnaire (RMDQ)
Time Frame: All participants: Baseline period weeks 0, 4, 8, 12; Intervention group: Intervention period weeks 0, 4, 8, 12, 16, 20, 24; Reference group: Monitoring period weeks 4, 12, 20, 24.
24-item self-report questionnaire used to determine the level of disability due to low-back pain. Items are rated as yes or no, with yes indicating that the responder endorses the statement as describing them today. Total score possible is 0-24, with scores indicative of the number of statements endorsed. The higher the total score, the more disabling the low-back pain.
All participants: Baseline period weeks 0, 4, 8, 12; Intervention group: Intervention period weeks 0, 4, 8, 12, 16, 20, 24; Reference group: Monitoring period weeks 4, 12, 20, 24.
Patient-Reported Outcomes Measurement Information System (PROMIS) Global Health-10
Time Frame: All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.
10-item self-report measure used to assess general domains of health and functioning including overall physical health, mental health, social health, pain, fatigue, and overall perceived quality of life. Nine items are rated on a scale of 1-5 with a variety of response options (e.g., poor to excellent or always to never). The lower the score the worse health across all 9 items. One item is rated on a scale of 0-10 with 0 being no pain and 10 being worst imaginable pain. Four of the 10 items are combined to create a global mental health raw score that ranges from 4 to 20. Similarity, four items are combined to create a global physical health raw score that also ranges from 4 to 20. Raw scores are converted to T-scores and higher scores indicate better mental or physical health. The remaining two items are used individually in analyses and are not included in the overall physical or mental health scores.
All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.
Orthotic and Prosthetic Users' Survey Satisfaction with Device (OPUS-SwD)
Time Frame: All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.
9-item self-report measure to assess satisfaction with device in persons who use prostheses. Items are rated 1-5 with 1 indicating strongly disagree and 5 indicating strongly agree. Total score possible is 9-45. The higher the score the better the satisfaction with device. The raw scores are converted to Rasch Measures.
All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.
Prosthesis Limb Users Survey-Mobility (PLUS-M)
Time Frame: All participants: Baseline period weeks 0, 4, 8, 12; Intervention group: Intervention period weeks 4, 8, 12, 16, 20, 24; Reference group: Monitoring period weeks 4, 12, 20, 24.
12-item self-report instrument for measuring mobility of adults with lower limb amputation (i.e., the ability to move intentionally and independently from one place to another). Items are rated on a scale from 1-5, with 1 indicating participants are unable to do the task and 5 indicating that participants can do it without any difficulty. Total raw scores range from 12-60. Raw scores are converted to a T-score using a lookup table, and final scores range from 20.3 to 67.7 on the T-score metric. The higher the total score the better the mobility.
All participants: Baseline period weeks 0, 4, 8, 12; Intervention group: Intervention period weeks 4, 8, 12, 16, 20, 24; Reference group: Monitoring period weeks 4, 12, 20, 24.
Patient-Reported Outcomes Measurement Information System (PROMIS) Ability to Participate in Social Roles
Time Frame: All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.
4-item self-report measure to assess satisfaction with one's usual social roles in life's situations and activities. These roles may exist in marital relationships, parental responsibilities, work responsibilities and social activities. Items are rated on a scale of 1-5 with 1 indicating participants always experienced the issue and 5 being never. Total raw score possible is 4-20. The raw score is converted to a t-score that ranges from 27.5 to 64.2 on the T-score metric. A higher score indicates better ability to participate in social roles.
All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.
Patient-Reported Outcomes Measurement Information System (PROMIS) Depression
Time Frame: All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.
4-item self-report measure used to assess depression. Items are rated on a scale of 1-5 with 1 indicating participants have never experienced the issue and 5 being always. Total raw scores range from 4-20 and are converted to T-scores using a lookup table. Final T-scores range from 41.0 to 79.4. A lower score indicates less depressive symptoms.
All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.
Charlson Comorbidity Index (CCI)
Time Frame: All participants: Baseline period week 0; Intervention/Monitoring period weeks 4, 24.
11-item self-report measure that assesses the presence of common health conditions. Items are rated as yes or no, with yes indicating participants have the health condition. Total score possible is 0-11. The higher the score, the more comorbid conditions the individual has.
All participants: Baseline period week 0; Intervention/Monitoring period weeks 4, 24.

Other Outcome Measures

Other Outcome Measures

For clinical trials, a planned measurement described in the protocol that is used to determine the effect of an intervention/treatment on participants. For observational studies, a measurement or observation that is used to describe patterns of diseases or traits, or associations with exposures, risk factors, or treatment. Types of outcome measures include primary outcome measure and secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Amputee Mobility Predictor with Prosthesis (AMP-Pro)
Time Frame: Intervention group only: Baseline period week 0; Intervention period weeks 0, 20.
21-item in-person performance-based measure that assesses mobility potential of people with a lower limb prosthesis that evaluates transfers, sitting and standing balance, and gait skills. Items are variably scored, and item scores can range from 0-1 to 0-5. Total score possible is 0-47. The higher the score, the higher the mobility category.
Intervention group only: Baseline period week 0; Intervention period weeks 0, 20.
International Society for Prosthetics and Orthotics (ISPO) Minimum Data Set for lower-limb prosthesis users involved Research Studies
Time Frame: Intervention group: Baseline period week 0; Intervention period week 0. Reference Group: Baseline period week 0.
Descriptive information about the participant and prosthesis will include all the variables recommended by ISPO in their data set for lower-limb prosthesis users involved in research studies. These include participant characteristics (eg, age, weight, amputation level, reason for amputation, time since amputation, prosthetic experience, residual limb shape categorization, residual limb sensation qualitative assessment, lower extremity joint range of motion, manual muscle testing of lower limb strength, previous history of gait training with a therapist, and assistive device use). The list also includes prosthesis characteristics: structural design of prosthesis, socket type, suspension, prosthetic foot, ankle, shank and knee components, and type of residual limb socks.
Intervention group: Baseline period week 0; Intervention period week 0. Reference Group: Baseline period week 0.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
University of Washington

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
Congressionally Directed Medical Research Programs

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Stefania Fatone, PhD, University of Washington

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
March 1, 2023

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
November 30, 2025

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
November 30, 2025

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
December 12, 2022

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
December 20, 2022

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
December 23, 2022

Study Record Updates

Last Update Posted (Estimated)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
December 15, 2025

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
December 9, 2025

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
December 1, 2025

More Information

Terms related to this study

Keywords

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • STUDY00015284
  • CDMRP-E03034.1a (Other Grant/Funding Number: Congressionally Directed Medical Research Programs)
  • CDMRP-E03034.1b (Other Grant/Funding Number: Congressionally Directed Medical Research Programs)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Data generated by this research will be made available to the research community and to the public via University of Washington ResearchWorks digital repository of scholarly work. Prior to sharing, data will be de-identified and redacted to reduce the risk of participant identification. Final research data will include the factual material necessary to document and support research findings such as the outcome measure results and participant characteristics upon which any accepted publications are based, it may include both raw data and derived variables. Documentation will also be provided regarding the procedures used to collect and analyze the data.

IPD Sharing Time Frame

Data will be shared no later than the acceptance for publication of the main findings from the final dataset.

IPD Sharing Access Criteria

ResearchWorks creates persistent URLs that will not change over time. A DOI can also be created. The URL or DOI will be included with all publications arising from this trial.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • ICF

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

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Cookie Settings

We use cookies to ensure that we give you the best experience on our website. For more details carefully read our Privacy and Cookies Policy. ...>>>You can change your preferences or withdraw your consent at any time by deleting the cookies from your website or computer as described in the policy. Please accept it and choose your preferences by ticking the corresponding boxes in the "Manage Settings" section below. Please carefully read our Terms of Service before you proceed with using any part of this website.
«Manage Settings