Pandemic response invalidated long-term outcome data collection

This clinical trial will compare how many days per year people with lower limb prosthesis do not wear their prosthesis when fitted with a conventional liner and a liner made with phase change materials.

Background: The proposed work will generate evidence-based practice guidance for temperature control liner technologies and allow providers to optimize care to Service members and Veterans with limb loss. Sizeable numbers of Service members and Veterans live with limb loss, mostly due to traumatic musculoskeletal injury. Addressing the resulting functional deficit with prostheses increases the risk for secondary conditions such as pressure sores, impaired blood perfusion, and injuries from accidental falls. Any of those occurrences can render the prosthesis temporarily useless, making it challenging for users to engage in many activities of daily life, including work, exercise, and social participation. Many of the described issues originate at the interface between residual limb and prosthetic socket, where the objectives of sufficient weight distribution and suspension are conflicting with the necessity to facilitate heat exchange and limit contact pressure and friction.

Recently, prosthesis liners that contain phase-change material have become commercially available, holding the promise that the micro climate at the interface between the residual limb skin and the prosthetic socket can be regulated to reduce the users' tendency to sweat. Preliminary studies on these liners indicate that the socket temperatures inside the socket stayed lower and rose slower than in conventional liners. However, the clinical relevance of those findings remains unclear. While (perceived) socket comfort is certainly an important criterion in prosthesis fitting, it may be claimed that only tangible functional benefits are of concern.

Objective/Hypothesis: The purpose of this study is to investigate whether longer (6+ months) periods of use of phase-change material based temperature control liners have clinically meaningful effects.

It is hypothesized that use of phase-change material infused liners will improve prosthesis utilization (measured in days of prostheses use per time), physical performance (measured by 2-minute walk test), and self-reported prosthesis related quality of life (assessed by questionnaire). The research follows the rationale that lower and steadier skin temperatures should result in reduced sweat, friction, skin damage, and prosthesis abandonment. This would encourage users to wear their prosthesis for longer periods of time and for an expanded array of purposes, thus increasing their ability to ambulate and to engage in a greater variety of activities.

Specific Aims:

1. To compare phase-change material liners to conventional liners with regard to activity and participation
2. To quantify the effect of phase-change material liners on prosthesis related quality of life and physical performance over time
3. To investigate the relationship between perceived benefits of phase-change material liners and patient-centric outcomes

Study Design: The proposed study will utilize a double-blind longitudinal cross-over research design. A sample of trans-tibial prosthesis users will be wearing their regular gel or silicone liners for six months and phase-change material liners for another six months in a randomized sequence. Their prostheses will be equipped with activity monitors, and participants will be asked to maintain a record of days when they could not wear their prosthesis due to any perceived issues with their residual limb or socket fit. In 1.5-month intervals, subjects' activity, physical performance, and overall prosthesis assessment will be recorded using standardized methods.

Inclusion Criteria:

• use of a prosthesis with liner suspension,
• at least one year of prosthesis use,
• a well-fitting socket,
• a matured residual limb (stable limb volume) that has not required socket modifications in the previous year,
• the ability to walk with the prosthesis outdoors without notable limitations (K-Level 3),
• stable weight,
• absence of acute medical conditions that would temporarily affect the ability to use prostheses.

Exclusion Criteria:

• use of a non-standard liner size,
• current use of a PCM liner as the regular suspension system,
• known allergies against liner materials,
• any inability to understand the protocol and to comply with the associated tasks, such as maintaining a log of days when the prosthesis could not be used.
• anticipated provision of a new prosthesis or extended (longer than one month) absences from the region during the study period

De-identified data may be shared in the future

1 year

Of the 42 participants that were enrolled (i.e., screened and signed the consent form), 36 received liners (19 received the PCM liner first and 17 received the regular liner first). After some attrition, 16 of the first group received the regular liner and ten of the second group received the PCM liner. Therefore, a total of 29 participants were exposed to the PCM liner and 33 to the regular liner during the study.

Covid-19 pandemic invalidated assumptions about the representativeness of daily step counts and led to early termination of enrollment and ongoing data collection. The remaining sample size was insufficient for the planned analyses beyond descriptive statistics.