Page 48 - JSOM Spring 2021

Results FIGURE 4 Average force for device compared to subject sex.
All statistical tests were performed using JMP statistical soft-
ware with a significance level of α = 0.05. We analyzed force
differences between the left and right FSRs on each subjects’
greater trochanters. A one-way ANOVA revealed no signifi-
cant differences between the left and right force values. Thus,
each subject’s left and right force values were averaged for the
remaining data analysis. While the team was able to analyze
the effect of different subject qualities (e.g., sex and body fat
percentage) on the force applied at the greater trochanters, it
was also important to determine whether force readings varied
based on device application by individual researchers. For all
compression devices, there was no significant difference (p =
.0728) identified among the researchers when comparing re-
sulting force applied to subjects’ greater trochanters. TABLE 1 Force versus Body Fat Percentage for All Devices
Male Female
Our initial hypothesis was that the commercial SAM Pelvic Devices r r² r r²
Sling would apply greater force to the pelvis than the impro- SAM Pelvic Sling II –0.07 0.0049 –0.224277 0.0503
vised pelvic compression devices would. Therefore, we used SAM Splint and C-A-T –0.428135 0.1833 0.1621727 0.0263
Student’s t-test to compare the greater trochanter force mea- SAM Splint and Cravat –0.368646 0.1359 –0.014142 0.0002
surements of the improvised devices with those of the SAM Cravat –0.294958 0.087 0.0479583 0.0023
Pelvic Sling (Figure 3). Interestingly, the magnitude of applied Belt –0.096437 0.0093 0.1264911 0.016
force of the SAM Splint and tourniquet was the greatest of
all devices; however, this was not statistically significant
compared with the SAM Pelvic Sling. As detailed in Figure Discussion
3, the belt exhibited significantly lower force characteristics Bottlang et al. laid the foundation for pelvic compression de-
26
(p = .0044) compared with the SAM Pelvic Sling. Addition- vice research with their 2002 cadaveric study (N = 7; 4 males,
ally, the SAM Splint and cravats were found to have a lower 3 females), which assessed external pelvic compression device
compressive force than the SAM Pelvic Sling. The SAM strap placement, force application, and computed tomogra-
Splint and tourniquet, and the cravats, did not demonstrate phy (CT)–verified pubic symphysis diastasis reduction in sta-
significant differences compared with the SAM Pelvic Sling ble and unstable pelvic fractures. According to the authors,
(p = .3728). when a prototype 50mm rubber strap was placed at the level
of the greater trochanters, an applied force of 180 ± 50 New-
FIGURE 3 Average comparison of compressive force by device.
tons (N), as determined by sensors integrated into the strap,
*p<0.05 effectively reduced unstable pelvic fractures without causing
significant internal rotation of lateral compression fractures.
*p<0.05
Bottlang et al. measured the tensile force required to reduce
26
the pubic diaphysis as visualized by CT. In contrast, our sensor
system assessed the direct normal compressive force applied to
the greater trochanters by the applied devices. This measure-
ment allowed us to acquire data and draw comparisons.
We initially hypothesized that the SAM Pelvic Sling would
generate the greatest pelvic compressive force; however, our
trials identified the SAM Splint and tourniquet, and the cra-
vats, as producing forces comparable to those of the SAM
®
Pelvic Sling. We believe that this may be secondary to the SAM
Pelvic Sling’s AUTOSTOP technology—alerting the end user
TQ = tourniquet.
*statistically significant to discontinue applying force when 150 N have been attained.
In contrast, the SAM Splint and tourniquet, and the cravats,
Next, we analyzed the force characteristics for each device were tightened to the greatest extent possible. Of all the de-
based on the subjects’ sex. The goal was to determine whether vices accessed, the standard-issue military belt was found to
there was a trend in force characteristics because the team have the smallest magnitude of applied force.
hypothesized that there would be no difference in applied
forces between the two sexes. As seen in Figure 4, applied Although this study examined compressive force, other factors
force readings from female subjects were greater than those may be considered when selecting a device for use in tactical
of male subjects; however, this was not statistically significant environments, such as material availability, component size
(p = .1323). and weight, and assembly time. For example, the SAM Pel-
vic Sling is currently issued to Air Force Pararescuemen for
Supporting our hypothesis, additional data analysis revealed external pelvic compression; however, given its size, it is in-
no strong correlation between body fat percentage and applied frequently carried in service members’ individual rucksacks.
pelvic compression device forces for male and female subjects The ability to improvise a device, both in the military and ci-
(Table 1). vilian sectors, may be vital during mass casualty events, where

46 | JSOM Volume 21, Edition 1 / Spring 2021