Page 98 - JSOM Fall 2023

hydration bladders could potentially be combined to grossly traditional leather-upper offloading devices called “axial resist
and hemodynamically stabilize larger extremity injuries. orthoses,” functioning to unweight the ankle and calcaneus via
a rigid frame that bypasses the foot and ankle and connects
Improvisation using vacuum splint techniques is limited due to the shoe. 61,65 Device design was improved by replacing the
to the nature of available materials and the need for a vacuum leather component with more rigid thermoplastic components,
apparatus. However, Air Force Pararescuemen carry a V-Vac resulting in several commercially available devices (Figure
45
suction system in their primary medical kit. This apparatus 5A). 52,53,55,61,66–72 These devices have an adjustable interface to
may be utilized with available materials, such as a waterproof simultaneously compensate for volumetric changes caused by
bag, standard to many field medical personnel, filled with swelling while applying compression to soft tissues and cir-
soft materials (e.g., clothing/gauze). This mirrors the granular cumventing the long bone fracture. Compression to the soft
jamming demonstrated in conventional vacuum splints. These tissues derives from principles associated with a patellar ten-
examples underscore the potential for creating innovative im- don-bearing prosthesis (PTB). The PTB was designed to apply
provised splinting techniques using materials available to com- loads through tissues in a transtibial residual limb that can
bat or wilderness units in PCC scenarios and the extant need tolerate loading (e.g., the tibialis anterior interosseous area be-
to evaluate the effectiveness of these designs. tween the tibia and fibula), while off-loading tissues that are
sensitive to pressure (e.g., crest of the tibia, proximal head of
the fibula). Current functional fracture orthotic interventions
Orthotic Interventions
reportedly increase patient satisfaction and reduce pain during
Functional fracture orthoses for definitive fracture man- ambulation (Figure 5B). 61–64,73,74 Further, many of these design
agement also highlight design features that could be used in features have been incorporated into more modern treatments,
splints developed for PCC scenarios (Figure 5). Functional such as the Intrepid Dynamic Exoskeleton Orthosis, for indi-
fracture orthoses accomplish stabilization by employing the viduals that have undergone complex limb salvage operations
principle of radial soft tissue compression around a long bone and wish to return to high-level activities, including return to
fracture. Further, these orthotic interventions incorporate ana- duty (Figure 5C). 75,76
tomic and mechanical support structures to off-load from the
fracture site, enabling weight bearing and encouraging mobil- The use of a functional femur fracture orthosis for compres-
ity. Functional fracture orthoses have demonstrated success in sion-based stabilization and off-loading of femur fractures
traditional, definitive orthotic care scenarios due to the ability presents challenges due to larger amounts of soft tissue sur-
to adjust to volumetric fluctuations. This has resulted in faster rounding the femur compared to that around the tibia. Yet,
healing rates and decreased monetary expense compared to designs developed for femoral fractures nevertheless rely on
plaster casting, while being less medically invasive than surgi- prosthetic off-loading design principles. By relying on the is-
cal fixation. 52–55 Notably, fracture orthoses are not designed to chial tuberosity of the pelvis in conjunction with a rigid struc-
eliminate interfragmentary motion because successful fracture ture running parallel to the intact leg and down to the ground,
healing is dependent upon achieving a specific mechanical en- ambulation has been achieved. The ischial tuberosity has been
vironment, wherein an optimal amount of interfragmentary used in both the Quadrilateral socket design from the 1950s
motion is allowed at the fracture site and controlled by the and the modern ischial containment socket prosthetic designs,
stiffness of a stabilization device. 56,57 Proper control of inter- intended for individuals with transfemoral amputation. 77,78 In-
fragmentary motion allows for the sustained vascularization corporating a proximal shelf that contacts the ischial tuberos-
in the fracture callous that is required for successful ossifica- ity of the pelvis reportedly off-loads the femoral shaft by 65%
tion. Fracture callous formation, critical to this fracture care and reduces loads on the femoral neck by 30% during walk-
58
technique, is achieved via flexible fracture fixation or stabili- ing, thus demonstrating the potential to utilize pelvic struc-
zation that allows for 0.2–1.0-mm interfragmentary motion at tures to off-load lower limb fractures in devices employed in
57
a fracture site displaced by 2-mm. In contrast to small axial austere environments. 79
deformations, shear displacement at the fracture site has been
shown to significantly delay facture healing, possibly leading Fracture orthoses have several design features that are applica-
to fracture non-union. 59,60 The use of fracture orthoses have ble to the development of devices capable of being employed
been primarily indicated in the management of low-energy in a PCC scenario, particularly in the absence of surgical stabi-
closed fractures of the tibia with >12-mm shortening and >5° lization. The use of circumferential pressure applied along the
angulation after reduction. Tibial fracture orthosis contra- limb segment through an adjustable interface may be sufficient
55
indications include presence of an intact fibula, polytrauma to limit interfragmentary motion while allowing volumetric
cases that prevent ambulation, or axially unstable fractures. 53,55 changes and access to wounded tissues. Utilizing the proximal
While most battlefield injuries to the extremities involve pol- tissues and a frame to bypass and off-load the injured tissues
ytrauma, in which a traditional fracture orthosis will be con- may provide opportunities for mobility after injury. The incor-
traindicated, there are multiple design features in fracture poration of energy storage and return components based on
orthoses that have applicability for enhanced mobility in PCC design features in the Intrepid Dynamic Exoskeleton. Orthosis
scenarios. If fracture care treatments within PCC scenarios can may also enhance this mobility.
also incorporate the optimal ranges of interfragmentary mo-
tion, then these PCC treatments may be complementary to de- Biomaterial Approaches to
finitive fracture treatment rendered after evacuation to higher Local Fracture Stabilization
echelons of care.
While providing external mechanical stabilization to fractures,
The evolution of current functional fracture orthoses was de- thereby enabling the injured person to bear weight, would
veloped out of a blending of prosthetic and orthotic design be a significant advancement in managing extremity injuries
principles in the mid-1900s (Figure 5). These designs started as within an austere environment, an opportunity also exists to

96 | JSOM Volume 23, Edition 3 / Fall 2023