Individuals with lower limb amputation often complain about uncomfortable residual limb skin temperatures and the accumulation of sweat inside their prostheses. It doesn't take long before the presence of sweat on the residual limb leads to a lack of confidence in the security of their prosthetic suspension. Some circumstances allow the wearer to doff the prosthesis before it falls off, wipe it and the residual limb dry, and then don it again. Another option is to simply reduce the intensity of activities before sweat becomes a problem. However, the Warfighter amputee may not be afforded such accommodations. For these service personnel, inadequate moisture management can significantly limit or inhibit their mobility. The objective of the proposed research is to provide lower limb amputees who work in demanding environments with a prosthesis that remains secure despite profuse residual limb sweating without compromising residual limb health and comfort.

The aim of this research is to compare three different, lower limb prosthetic suspension systems and identify which is most effective at maintaining a secure adherence when worn in conditions that result in profuse sweating. The investigators also aim to compare how the three study prostheses effect residual limb skin health and comfort when participants pursue their usual activities in the home, work, and community environments.

To achieve these aims, the investigators will to recruit 25 below-knee amputees. Each subject will be asked to be asked to wear: (1) their as-prescribed prosthesis, (2) a prosthesis with a perforated elastomeric liner that allows sweat to flow away from the skin, and (3) a prosthesis that has a battery and body-weight activated pump to flow air between the prosthesis and the residual limb skin, allowing expulsion of any accumulated sweat. Subjects will wear each of these prostheses in the home, work, and community environments for two weeks, after which the investigators will measure their residual limb health and comfort. Subjects will then walk on a treadmill in a room whose climate will be set to Middle East-like conditions: 35 °C (95 °F) and 50% relative humidity. After 30 minutes, the investigators will measure any slippage of their prosthesis relative to their limb and how much sweat is expelled. The investigators hypothesize there will be differences in the amount of slippage, residual limb health, and comfort between the three prostheses.

Individuals with lower limb amputation often complain about uncomfortable residual limb skin temperatures, accumulation of perspiration inside their prostheses, and loss of confidence in suspension security that often leads them to cease their activities or, in demanding circumstances, may lead to their prosthesis falling off. Most amputees can sense the impending loss of suspension during vigorous activities and can stop, doff the prosthesis, wipe it and the residual limb dry, and then don it again. However, the Warfighter amputee may not be afforded such accommodations.

The investigators will compare the performance of an individual's as-prescribed suspension with two exciting alternatives: a new-to-market liner intended to transport perspiration away from the skin and an improved version of the Dynamic Air Exchange (DAE) suspension system the investigators developed. The new-to-market suspension system consists of a perforated elastomeric liner that allows perspiration to be exuded into the liner-prosthesis space. Anecdotal reports suggest this liner (Uniprox's SoftSkin Air), can maintain suspension during profuse perspiration, but may result in excessive skin dryness and discomfort. The improved Dynamic Air Exchange - Rising Edge Design (DAE-RED) suspension expels accumulated perspiration using a vacuum pump like its predecessor, but incorporates hybrid, body-weight activated pump to minimize battery consumption and a revised ventilation system obviating the need for undesirable exterior tube connections.

The objective of the proposed research is to provide lower limb amputees who work in demanding environments with a prosthesis that remains secure despite profuse residual limb perspiration without compromising residual limb health and comfort.

The proposed research has two specific aims: (1) compare three different, lower limb prosthetic suspension systems and identify which is most effective at maintaining a secure adherence when worn in conditions that result in profuse perspiration, and (2) compare how the three suspension systems effect residual limb skin health and comfort when participants pursue their usual activities in the home, work, and community environments.

The investigators will recruit unilateral transtibial amputees who are successful ambulators on their as-prescribed prosthesis and collect baseline data (residual limb skin hydration, transepidermal water loss (skin barrier function), and Socket Comfort Score). After fitting the participants with Uniprox and DAE-RED prostheses, subjects will wear one of these study prostheses (random order) for two weeks, after which the investigators will measure their skin hydration, transepidermal water loss, and Socket Comfort Score. The subject will then enter our environmental chamber (35° C and 50% relative humidity) and sit for a 30-minute acclimation period. The subject will then walk for 30 minutes on a treadmill at their self-selected speed. Subjects will then exit the environmental chamber and sit for 30 minutes in a comfortable climate (~20° C and 50% relative humidity). The amount of slippage, along with the perspiration accumulated/expelled, will be then be measured. Subjects will then be fit with their as-prescribed prosthesis and the protocol repeated to washout intervention effects. Finally, subjects will be fit with the other study prosthesis (either Uniprox or DAE-RED) and repeat the protocol.

After wearing the prostheses in our environmental chamber set to Middle East-like conditions (35 °C and 50% relative humidity), the investigators hypothesize:

H1.1 The amount of slippage (loss of adherence) will be different between the three suspension systems.

H1.2 The amount of perspiration expelled will be different between the Uniprox and DAE-RED.

After wearing the study prostheses in the home, work, and community environments for two weeks, the investigators hypothesize:

H2.1 Residual limb skin hydration will be different between the three suspension systems.

H2.2 Residual limb transepidermal water loss will be different between the three suspension systems.

H2.3 The Socket Comfort Score will be different between the three suspension systems.

Inclusion Criteria:

• Unilateral transtibial amputation
• Been fit with a prosthesis and used it for at least six months
• Wear the prosthesis for four or more ours on an average day
• Ambulate without upper extremity aids
• Able to walk for 30 minutes on a treadmill

Exclusion Criteria:

• Improper fit and suspension with current prosthesis and one cannot be achieved with clinical resources (determined at initial visit)
• Current skin irritation or injury on residual limb
• Osteoarthritis, injury, or pain that interferes with walking ability
• Currently incarcerated
• Pregnant (determined via self-report)
• Inadequate cognitive function or language proficiency to consent to participate
• High (>20%) coronary heart disease risk at 10 years as determined by heir Framingham Risk Score

A de-identified, anonymized dataset in machine-readable format will be created and shared for all individual participant data (IPD) that underlie results in a publication. The investigators will follow 164.514(a) of the HIPAA Privacy Rule for de-identification of IPD.

Within six months after publication of final study findings.

Open access through Pubmed Central, SimTk, PhysioNet, or other similar open-source data repository websites. The investigators will work with manuscript publishers when possible to link the final study data sets to an appendix or supplemental materials on the publisher websites.

6 weeks