AzTrials
AzTrials

Transfemoral AmputationNCT05662982

Sub-Ischial Socket for Transfemoral Amputation and Lower Mobility

A study testing Northwestern University Flexible Subischial Suction Socket (NU-FlexSIS) in people with Transfemoral Amputation, run by University of Washington at 3 sites in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
Search all trials

Trial summary

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… Read more about this study

Who is it for?
Ages 18 years and older
Conditions the study is for
Transfemoral Amputation
What is being tested?
Northwestern University Flexible Subischial Suction Socket (NU-FlexSIS)
Type of treatment
Medical device
Could I receive a placebo?
No, everyone receives an active treatment
How many people
84 participants
Where
3 sitesUnited States
Study dates
1 Mar 2023to 30 Nov 2025
Phase
Interventional
Are there results?
None posted in the registry

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

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

Who cannot join

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

Trial locations and contacts

3 sites in 1 country.

United States3 sites
  • Hanger Institute for Clinical Research and Education

    Houston, Texas, 78758

  • Minneapolis VA Health Care System

    Minneapolis, Minnesota, 55417

  • University of Washington

    Seattle, Washington, 98195

Other trials in United States

About this study

Official title: 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.

Read the 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.

Being tested
Northwestern University Flexible Subischial Suction Socket (NU-FlexSIS)
Keywords
prosthesis, prosthetic socket

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • Northwestern University Flexible Subischial Suction Socket (NU-FlexSIS)Device

    A custom-made prosthetic socket for transfemoral amputation that consists of proximal trimlines that do not interact with the pelvis.

Study groups in NCT05662982
Study groupRoleWhat they receive
Intervention GroupExperimentalParticipants 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.
Receives: Device: Northwestern University Flexible Subischial Suction Socket (NU-FlexSIS)
Reference GroupNo interventionParticipants will be assessed for 40 weeks in their usual ischial containment socket. No intervention will be provided.

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Change in Socket Comfort Score (SCS)

    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.

    Measured: Change from week 12 to week 24 compared between Intervention and Reference Groups.

Secondary outcomes (12)
  1. Temperature sensor

    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.

    Measured: Intervention group only: Baseline period weeks 0-12; Intervention period weeks 0-24.

  2. Step counter

    A step counter activity monitor is an ankle-worn, microprocessor-controlled, two-dimensional accelerometer that measures step counts and step rates per unit time.

    Measured: Intervention group only: Baseline period weeks 0-4; Intervention period weeks 0-4 and 20-24.

  3. Prosthesis Limb Users Survey-Mobility (PLUS-M)

    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.

    Measured: 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.

  4. Activities-specific Balance Confidence (ABC) Scale

    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.

    Measured: 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.

  5. Prosthesis Evaluation Questionnaire (PEQ) Residual Limb Health

    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.

    Measured: 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. Roland-Morris Disability Questionnaire (RMDQ)

    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.

    Measured: 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.

  7. Patient-Reported Outcomes Measurement Information System (PROMIS) Ability to Participate in Social Roles

    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.

    Measured: All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.

  8. Patient-Reported Outcomes Measurement Information System (PROMIS) Global Health-10

    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.

    Measured: All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.

  9. Patient-Reported Outcomes Measurement Information System (PROMIS) Depression

    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.

    Measured: All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.

  10. Orthotic and Prosthetic Users' Survey Satisfaction with Device (OPUS-SwD)

    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.

    Measured: All participants: Baseline period weeks 0, 12; Intervention/Monitoring period weeks 4, 12, 24.

  11. Charlson Comorbidity Index (CCI)

    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.

    Measured: All participants: Baseline period week 0; Intervention/Monitoring period weeks 4, 24.

  12. Falls

    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.

    Measured: 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.

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted23 Dec 2022
  2. Study start1 Mar 2023
  3. Primary completion30 Nov 2025
  4. Study completion30 Nov 2025

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase N/A
Primary purpose
Treatment
Allocation
Non-randomised
Intervention model
Parallel groups
Model description
Two independent groups will be assessed longitudinally over 40 weeks: one group will be assessed using only the standard of care ischial containment socket and the other group will receive the subischial socket.
Masking
None (open label)
Enrolment
84 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT05662982
Sponsor's protocol ID
STUDY00015284
Other IDs
CDMRP-E03034.1a, CDMRP-E03034.1b
Status last verified
Dec 2025
First submitted
12 Dec 2022
Last updated
15 Dec 2025
Results posted
No
Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
Yes
Individual data sharing
Yes: 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.

Publications

  • Fatone S, Caldwell R. Northwestern University Flexible Subischial Vacuum Socket for persons with transfemoral amputation-Part 1: Description of technique. Prosthet Orthot Int. 2017 Jun;41(3):237-245. doi: 10.1177/0309364616685229. Epub 2017 Jan 17.

    PubMed 28094686
  • Caldwell R, Fatone S. Technique modifications for a suction suspension version of the Northwestern University Flexible Sub-Ischial Vacuum socket: The Northwestern University Flexible Sub-Ischial Suction socket. Prosthet Orthot Int. 2019 Apr;43(2):233-239. doi: 10.1177/0309364618798869. Epub 2018 Sep 17.

    PubMed 30223715
  • Fatone S, Caldwell R, Angelico J, Stine R, Kim KY, Gard S, Oros M. Comparison of Ischial Containment and Subischial Sockets on Comfort, Function, Quality of Life, and Satisfaction With Device in Persons With Unilateral Transfemoral Amputation: A Randomized Crossover Trial. Arch Phys Med Rehabil. 2021 Nov;102(11):2063-2073.e2. doi: 10.1016/j.apmr.2021.05.016. Epub 2021 Jun 29.

    PubMed 34214499
  • Fatone S, Stine R, Caldwell R, Angelico J, Gard SA, Oros M, Major MJ. Comparison of Ischial Containment and Subischial Sockets Effect on Gait Biomechanics in People With Transfemoral Amputation: A Randomized Crossover Trial. Arch Phys Med Rehabil. 2022 Aug;103(8):1515-1523. doi: 10.1016/j.apmr.2022.02.013. Epub 2022 Mar 13.

    PubMed 35296398

Questions about this trial

What is this clinical trial studying?

A study testing Northwestern University Flexible Subischial Suction Socket (NU-FlexSIS) in people with Transfemoral Amputation, run by University of Washington at 3 sites in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 13 inclusion and 7 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 15 Dec 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 3 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Change in Socket Comfort Score (SCS) (time frame: Change from week 12 to week 24 compared between Intervention and Reference Groups.). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05662982, which also lists 4 linked publications.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 15 Dec 2025; AzTrials last refreshed its copy on 29 Oct 2026.

Free account

Keep searching with a free account

You’ve used your 3 free searches for this session. Log in or create a free AzTrials account to keep searching clinical trials and save the ones you want to follow.

Create a free accountLog in