The comfort and fit of the residual limb within a prosthetic socket are of primary concern for many amputees. The residual limb is typically covered by non-breathable and non- thermally conductive materials that can create a warm and ultimately moist environment.

To address this, Liberating Technologies, Inc. (LTI) and Vivonics, Inc. have developed a thermo-electric cooling (TEC)-based module called the Intrasocket Cooling Element (ICE), that can be embedded into the prosthesis in order to cool the residual limb. A technology that can provide thermal control while retaining adequate suspension, weight and other prosthetic characteristics would benefit many prosthesis wearers.

The comfort and fit of the residual limb within a prosthetic socket are of primary concern for many amputees. The residual limb is typically covered by non-breathable and non- thermally conductive materials that can create a warm and ultimately moist environment. Studies found increases in socket temperature after the prosthesis was donned (0.8 degrees C) and after 30 minutes of walking (2.5 degrees C). Temperatures were found to remain elevated long after activity cessation and even a rest period of double the duration of the preceding activity period is insufficient to return the limb to its initial temperature. A study suggested that a modest temperature increase of only 2 degrees C may be responsible for reports of thermal discomfort by amputees. Therefore, a small amount of activity can cause the socket temperature to elevate and remain at an uncomfortable level for an extended period of time, which can lead to decreased wear times. In summary, an uncomfortable socket/residual limb interface decreases prosthesis use among amputees who want to remain active in their lives.

To address this, Liberating Technologies, Inc. (LTI) and Vivonics, Inc. have developed a thermo-electric cooling (TEC)-based module called the Intrasocket Cooling Element (ICE), that can be embedded into the prosthesis in order to cool the residual limb. A technology that can provide thermal control while retaining adequate suspension, weight and other prosthetic characteristics would benefit many prosthesis wearers.

This study will focus on investigating the efficacy of this novel socket cooling technology.

The rationale for this study is to determine how well the new technology can cool the residual limb not only in a controlled laboratory environment, but also in a home environment where the device would ultimately be utilized.

The primary objective of this study is to measure the effects of cooling the residual limb on quality of life (QoL) and functional outcomes. Cooling the residual limb inside the prosthetic socket would result in less sweating and greater comfort while wearing the prosthesis, and ultimately greater function and better quality of life as measured by standard functional and QoL outcome measures.

A two group, prospective, double-blinded, block randomized, crossover study design will be implemented. Research participants will be consented and have baseline activity and socket temperature data collected from their usual prosthesis during normal use (4 weeks). The ICE system will be integrated into a custom, experimental socket for each subject. Two versions of the cooling module will be created: (1) a fully-functional, active ICE cooling module (the so called "ON", or experimental, condition), and (2) a placebo ICE module with the TEC unit replaced with an insulating material layer between the fan and the heat spreader such that even when the system is turned on, minimal heat transfer occurs (the control, or "OFF" condition). An ICE module with a heat spreader will be embedded into the socket and the fan will continue to run whether or not active cooling is engaged for both test conditions; however, no heat will be able to be transferred through the insulating layer in the OFF condition. The TEC inside the ICE unit will not be visible once assembled and the modules will be assembled independently; therefore, both the subject and the tester will be blinded to the condition being tested for both the in-lab and at-home testing. A serial number will be used to identify the assembled units and the master key stored separately.

The participants will be divided into two groups and the order of the experimental conditions will be randomized. Each condition will be tested for 4 weeks. In-lab testing and functional measures will be assessed between testing periods as additional assessments of efficacy of the device. Testing will consist of 4 test site visits, as well as 1-2 visits to create and align the experimental socket. The entire study will continue for 3 months.

Lower limb prosthesis users will be recruited for the study and consented with an approved protocol. Research participants will represent a convenience sample and will reflect the local population of both above-knee (AK) and below-knee (BK) amputees of various K-levels using a variety of suspension types who could benefit from temperature control within the socket.

A maximum of 20 subjects will be recruited for this study. This is increased from the target 16 subjects to account for any drop-outs, etc.

Inclusion Criteria:

• Must have a lower limb absence
• Willing and able to complete outlined tasks
• Must complete and pass our Semmes-Weinstein monofilament test
• Must understand English in order to be properly consented and provide feedback to the study personnel

Exclusion Criteria:

• The risks to pregnant women and fetuses are unknown and therefore pregnant women should not participate in the study
• No symptoms consistent with peripheral neuropathy or other sensory diagnosis that could prevent them from feeling the temperature of their limb

Adverse events were monitored/collected during the experimental conditions. With each condition lasting about 1 month, each participant was monitored for adverse events for about 2 months. Adverse events were monitored/assessed at least every 2 weeks by phone call, with study staff checking in more frequently if participants reached out with questions. Participants were told to reach out to study staff immediately if adverse events did occur.