Socket Cooling Effectiveness Take Home Study

Continuation of the Development of Moisture Management Liner and Active Cooling System for Improving Residual Limb Skin Care

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.

Amputation, Amputation; Traumatic, Leg, Lower, Amputation Stump, Limb; Absence, Congenital, Lower, Prosthesis User, Lower Limb Amputation Below Knee (Injury)

cooling, amputee, lower limb absence, prosthesis, prosthetic leg, transtibial, below knee amputation, lower limb difference, lower limb loss, socket, prosthetist, sweat, active, walking, prosthetic liner, prosthetic sock, perspiration, moisture, heat, thermal

The subject wears their usual socket with an ambient temperature sensor and step counter for approximately one month.

The subject wears the experimental socket with an ICE Unit, which includes a TEC and will be actively cooling the leg whenever the device is powered on. An ambient temperature sensor and step counter is attached to the socket. The subject is only informed that each condition is a "different level of cooling" to reduce bias. This condition should last approximately one month.

The subject wears the experimental socket with a Sham Unit, which excludes a TEC and will not be actively cooling the leg when the device is powered on. An ambient temperature sensor and step counter is attached to the socket. The subject is only informed that each condition is a "different level of cooling" to reduce bias. This condition should last approximately one month.

Experimental socket integrated with a heat spreader. An ICE Unit (includes TEC) is attached to the socket.

Experimental socket integrated with a heat spreader. A Sham Unit (excludes TEC) is attached to the socket.

This will be tested only during in-lab visits. An intervention of the experimental socket with the ICE cooling unit should yield at least a 2 degree Celsius decrease in temperature compared with no intervention. This will be tested in-lab with 6 thermocouples taped to the residual limb while the subject is sitting and walking on a treadmill.

A custom survey regarding user satisfaction will be completed for all 3 conditions of the study (baseline, ICE unit, SHAM unit). This custom questionnaire uses a 5 point Likert scale (1-5) and will be used to rate different aspects of each condition.

This will be tested only during in-lab visits. After the subject has completed a condition of sitting and walking, the subject will remove their socket and liner. Immediately after removal, the inside of the liner will be wiped down by an absorbing material (pad) and placed on a high precision scale to document any weight added to materials (pad, gloves) due to sweat absorption. This is measured in grams.

Over the course of the entire study, a log book will be kept by the subject to document if they feel the condition is better or worse than their usual non-cooling socket and liner. The data will be qualitative. The subject will discuss if they felt their socket cool down, if they were able to do any activities their normal socket wouldn't have allowed them to complete, if the experimental socket allowed more suspension during high-intensity activities than their usual socket, as well as anything else they would like to note so the investigators have a better understanding of their experience.

The version of the PEQ which will be administered consists of 22 questions in 6 categories. Each PEQ question is normally administered on a VAS (0-100), but was instead placed on a Likert scale from 1-5.. The decision was made to convert the questionnaire results back to the VAS Scale range (1=0, 2=25, 3=50, 4=75, 5=100).

PROMIS Short form 4a and 8a were selected to help evaluate the subject's activities and social roles. Short form 4a focuses on "Satisfaction with Social Roles and Activities". Short form 8a focuses on the Subjects "Ability to Participate in Social Roles and Activities". The questions are answered on a scale from 1-5 and add up to a sum "raw-score" which correlates to a T-score and standard error.

The 12 question PLUS-M survey gauges the user's mobility in their daily life for each condition. The questions are answered on a scale from 1-5 and add up to a sum "raw-score" which correlates to a T-score and standard error.

This survey asks the user to rate the comfort of their socket on a 0-10 scale where 0 is the most uncomfortable and 10 is the most comfortable socket imaginable.

The Dermatology Life Quality Index is a simple questionnaire designed to measure the health-related quality of life of adult patients suffering from various skin diseases. A modified version of the questionnaire was created to be more directly applicable to persons with amputation. The modified survey can have a score from 0 to 27, with lower numbers indicating a better outcome. Scores on the unmodified DLQI of 0-1 indicate no affect at all from a skin condition on a patient's life. Score ranges of 2-5, 6-10, 11-20 and 21-30 are considered to have 'small,' 'moderate,' 'very large,' and 'extremely large' effects on a patient's life, respectively.

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