Sub-Ischial Socket for Transfemoral Amputation and Lower Mobility

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.

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.

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.