Development of Adaptive Vacuum Suspension to Improve Prosthetic Fit and Residual Limb Health

The purpose of the study is to evaluate residual limb circulation and skin health associated with the use of a prosthetic vacuum socket. A conventional non-vacuum prosthetic socket will be compared to a vacuum prosthetic socket.

The prosthetic suspension plays a pivotal role in an amputee's comfort. It can also significantly impact an amputee's limb health. If the prosthesis is not held securely to the amputee's limb, relative movement between the limb and prosthetic interface can cause bruising, skin irritation and skin breakdown. These poor outcomes are uncomfortable and can lead to much more serious health conditions. A positive solution to creating secure and comfortable suspension is the use of a vacuum suspension socket. The vacuum pressure assists in preventing movement in the socket. The clinical benefits associated with vacuum suspension include volume retention, increased proprioception, secure suspension, and frequently reported observations of wound healing. However, the long term effects of vacuum suspension on circulation remain undetermined or undocumented. This study examines a vacuum suspension system on the health of the residual limb (amputated limb). A vacuum socket creates a vacuum between the rigid prosthetic socket and prosthetic liner which is sealed to the socket. Therefore, vacuum is not directly applied to the skin of the residual limb.

There are a total of 3 study visits, (some visits may be broken into separate visits per preference of subject), including socket fitting visits (which could be 2 separate visits), a baseline visit, and a final visit. During the socket visit, which may consist of a three visits plus socket adjustments (as needed by the participant) on separate days (up to 4 weeks), limb shape capture, measurement or tracing, diagnostic static fitting and diagnostic static fitting, and delivery of a definitive "research" socket will be done. At the baseline visit, participants will perform seated tasks, standing tasks, and treadmill walking tasks. Residual limb health measurements will be taken before and after the activity period, including surface electrical capacitance, Transepidermal Water Loss (TEWL) measurement, hyperspectral imaging, Hitachi Aloka ultrasound imaging, Blood Flow, and digital imaging during the baseline visit as well. The final visit, using the research socket, will consist of the same tasks and measurements as the baseline visit and questionnaires will be completed. The subject may choose to break up the final visit tasks into 2 different visits if desired.

After completion of the study, participants will be given the choice to keep the research socket or return to using their original prosthesis as normal. The study prosthetist will be available to review and adjust the fit of their standard of care prosthesis at this time. Note: Due to physical change and limb volume fluctuation over the study period, it is possible that at the end of the study the standard of care prosthesis will not fit your residual limb as it does at the beginning of the study. At the completion of the study, it is recommended that the subject follow up with their primary care prosthetist for socket evaluation and fitting.

There may be risks that are not known about at this time. Side effects, risks, and discomforts may result from study participation .While the goal of this project is to create a more comfortable prosthesis, it is possible that the subject could experience discomforts commonly associated with prosthesis use, such as perspiration, dry skin, rash, itching, blisters, high pressure in the socket, looseness in the socket, and mechanical rubbing that leads to ulceration which may lead to infection and additional surgery. Subjects with low levels of arterial blood flow have an additional risk of ulceration.

* Prosthesis placement: While the goal of this project is to create a more comfortable prosthesis, it is possible that the subject could experience discomforts commonly associated with prosthesis use, such as perspiration, dry skin, rash, itching, blisters, high pressure in the socket, looseness in the socket, and mechanical rubbing that leads to ulceration.
* Treadmill task:There is a risk of falling during the research activities. This risk is mitigated by the ability of participants to self-select pace for the treadmill task and observation of treadmill activities by research staff.
* Transcutaneous Oxygen Measurement (TcOM) and skin temperature: The PeriFlux System 5000 uses non-invasive probes that will measure the skin temperature and transcutaneous Oxygen Measurement and poses minimal risk to the subject. The probe head is affixed to the residual limb by an adhesive sticker. Removal of the sticker after data acquisition may cause minor discomfort similar to removing a small band-aid.
* Hyperspectral Imaging: This non-invasive imaging technique poses minimal risk to the subject. A small fiduciary marker sticker is placed on the subject's limb to calibrate camera settings. Removal of the sticker after imaging may cause minor discomfort similar to removing a small band-aid.
* Hitachi Aloka Ultrasound:Ultrasound imaging is a noninvasive technique and is a minimal risk procedure.
* TEWL and Surface Electrical Capacitance Measurements: TEWL and Surface Electrical Capacitance measurements are noninvasive and propose less than minimal risk.

Subjects will be queried on self-reported measures of user comfort and performance. Briefly, four subjective measures will be completed: VR-36, PEQ, SCS, and measures from the NIH PROMIS

The CHAMP test will be used to assess overall amputee performance and the effect of the socket suspension intervention over time. The conglomeration of clinical assessment tools into the CHAMP was specifically done to measure high-level mobility in service members with a lower limb amputation. CHAMP consists of the Single Leg Stance Test (SLS), the Edgren Side Step Test (ESST), Illinois Agility Test (IAT), and T Test.

IU Neuroscience Gait lab will be used to collect kinematic data. The laboratory is equipped with an instrumented treadmill and infrared camera system. A harness system will be used to provide support and safety for the amputees while study participants walk on the treadmill for 6 minutes.

Eligibility Criteria:
Inclusion Criteria:

* Ages of 18 and above
* Unilateral transtibial or transfemoral amputee
* Ambulate at a K2 level or higher
* At least 3 months post-amputation per physician discretion
* Residual limb length greater than 6.5 inches in length
* Able to follow directions and give informed consent on their own or through Legally Authorized Representative.
* Must be able to ambulate without assistance. An external assistance device such as cane or walker will be permitted.
* Adequate arterial blood flow as evidenced by a TcOM \>30mmHg measured within the past 12 months.

Exclusion Criteria:

* Conditions that prevent wearing a prosthetic socket,such as existing scab, ulcer, or keloid scar on amputation stump.
* Cognitive deficits or mental health problems that would limit ability to consent and participate fully in the study protocol
* Women who are pregnant or who plan to become pregnant in the near future