A total of 13 adult human subjects (12 male and 1 female) were enrolled in this study. One participant was only part of the pilot run and not the formal data collection phase. Two subjects were withdrawn from study. Of the two withdrawn, one was unable to wear the research liner for longer durations of time because of skin irritations. The other subject was withdrawn because of a personal medical condition. Ten participants completed all protocol procedures. One was excluded from data analysis due to a protocol deviation. Therefore, data analysis was performed on a total of 9 subjects, 8 males and 1 female with mean age of 46 ± 14 years. Reasons for amputation were trauma and infection. Time since amputation varied from 15 years to under a year. Eight subjects were a K3 level while one was a K2 activity level (Table 1). Two adverse events (AE) were reported during the study period of these one was determined to be unrelated while the other AE was related to developing skin irritation with the use of Investigational device, the AE resolved and the participation for this subject (AE-10) ended.
The vented system (VS) significantly attenuated relative humidity (RH) and no change in temperature on the skin liner interface following activity in a climate-controlled room. Each session for determination of RH lasted 1 hour and 25 minutes and occurred in an ambient temperature room (T:21°C ± 1°C, H:41%±2%) followed by performing activities in a heated room (T:30°C ± 1°C, H:54%±6%) then post activity return-back to the ambient temperature room (Fig. 1d). The data from residual limb and sound side limb have been presented as continuous recording of RH as a function of time (Fig. 2a, b). There was no significant change in the baseline humidity both on residual limb (Fig. 2a) and sound side (Fig. 2b) as shown by the representative plots. However, during activity the humidity was significantly elevated compared to baseline (Fig. 2c) on the residual limb side as compared to sound side (Fig. 2d). The average RH during activity was significantly attenuated in residual limbs with the use of VS as compared to nVS (Fig. 2c).
The RH environmental data collected simultaneously with the RH from skin-liner interface confirmed that the reduction in RH at the skin interface was not due to changes in environmental conditions. The conditions were comparable in both VS and nVS grouVS (Fig. 3). Representative continuous recordings and average of environmental relative humidity (Fig. 3a, b) and temperature (Fig. 3c,d) of the study rooms has been presented to show consistent levels.
To further investigate the humidity change during activity, AUC was computed using a trapezoidal
integration algorithm by implementing a locally written MATLAB® code. The representative relative humidity-time graph highlighting the region considered is shown (Fig. 4a). The results show that the AUC-based percent reduction in humidity by the vented socket-liner solution was 30 ± 12.50% and highly significant (p < 0.0002; in AUC reduction between VS and nVS (Fig. 4b).
During activity, an increase in temperatures within socket has been reported to result in discomfort. Interesting, current study noted no significant increase in the in-socket temperatures on the residual limb (nVS vs VS) or skin temperature in the sound limb side suggesting adequate thermoregulatory processes keeping the skin temperatures unchanged.
A significant reduction in perceived sweating following the use of VS as compared to nVS. Perceived sweat was one of the secondary outcomes. Subjects rated their perceived sweat during activity on a scale from 1–10 where 1 is an extreme amount of sweat, and 10 is no sweat at all. A higher score corresponds to less perceived sweat on the skin. A paired, one-sample, two-tailed t-test was used to compare perceived sweat ratings between the VS and nVS (p = 0.028, 95% CI [0.12, 3.88], Fig. 4c). The temperature measured in-socket of investigational vented liner-socket system (Fig. 5a,c) were not significantly different compared to the conventional non-vented system. Likewise, the environmental temperature was well maintained (Fig. 5b,d) during the study period.
The investigational VS did not significantly affect perceived stability, suspension or comfort. The Comprehensive Lower Limb Amputee Socket Survey (CLASS) is a self-report measure of prosthetic socket satisfaction that quantifies suspension, stability, comfort and appearance14. The scale is 1–4, from strongly disagree to strongly agree, 0 is not applicable. CLASS stability subsection was used to evaluate perceived stability. One-tailed Wilcoxon-signed rank test was used to determine whether the median of CLASS stability score of VS compared to nVS, was no worse. The significance level was set at p < 0.0167 and margin of non-inferiority (d) was − 7% (-0.07). The median was 0.063 and 98.33% CI was (-0.031, Inf). The CI does cross intervention difference of 0 but not the margin of noninferiority (Table 2). The VS and nVS are not different with respect to perceived stability during increased perspiration. A table summarizing and mean ± SD and statistical significance of all endpoints have been presented (Table 3).