The objective of the proposed research is to provide the Warfighter with a below-knee amputation a prosthesis that best addresses problems of perspiration and its accumulation inside the prosthesis. A concern of every individual with a lower limb prosthesis is keeping their residual limb healthy and injury free. Naturally occurring perspiration, induced by moderate to vigorous activity or hot and humid environments, leads to perspiration. While the modern prosthetic liner can be stable, secure, and comfortable when dry, the materials from which they are made trap heat and are impermeable to moisture. When perspiration accumulation is a frequent occurrence, a host of biomechanical and skin problems can arise. Clinicians have few available options to prevent perspiration accumulation inside the prosthesis.

For individuals who do have problems with residual limb perspiration, some may be able to stop their activity when it accumulates, remove their prosthesis, dry it and their residual limb, then don it again and carry on. Others, like the Warfighter, may not have such an opportunity. These individuals can be prescribed a perforated liner through which perspiration can drain, or a thin, special purpose half-ply sock worn between the skin and liner, which can reduce the lubricating effects of perspiration. Current commercially available perforated liners come with two different sized holes: one with small holes the size of a pinprick, and one with somewhat larger holes the size of a pinhead. There is little evidence available to suggest which of the three approaches is best.

The aim of the proposed research is to compare these three clinically available options and determine which is best at addressing the problem of perspiration accumulation inside the prosthesis. To achieve this aim, we propose to recruit 180 individuals with below-knee amputations to participate in a human subject experiment. Eligible individuals will be ambulatory, report problems with perspiration, and currently wear one of two common liners (either the Alpha Classic or Alpha Hybrid [WillowWood, Mt. Sterling, Ohio]). Usually wearing a different liner requires the fitting of a new prosthetic socket because liners have quite different thicknesses and profiles. For this study, we propose to avoid using the usual process of in-person visits to reduce study-related COVID-19 exposure risks. Instead, we have developed a novel method to perforate liners such that they are physically like the two commercially available perforated liners. However, the method only works on thermoplastic elastomer liners like the Alpha Classic and Alpha Hybrid. We will use liner serial numbers to identify and order duplicate liners, which we will perforate.

We plan to recruit nation-wide because no clinical visits will be required. Upon enrollment, we will identify which liner participants are wearing and administer a survey to measure the stability, suspension, and comfort of their socket. Subjects will then receive one of three study-provided liners: (1) a liner-liner, (2) a liner perforated with small holes, or (3) a liner perforated with large holes. After subjects have worn the study-provided liner for 2 weeks, we will administer the survey again. The results of this research will identify which of the three clinically available options is best at addressing the problem of perspiration accumulation inside the prosthesis.

More than half a million Americans live with a lower limb amputation, and a few thousand of these were on active duty when it happened. For the many individuals with a lower limb amputation who have problems with perspiration, the results of this 2-year study will be of value as it will help them, and their clinicians, choose the best commercially available solution.