Biomechanical substantiation of the use of rod external fixation devices in the treatment of wounded with gunshot fractures of long bones of the extremities

today, the treatment of wounded with gunshot fractures of long bones of the extremities is the most important task of military traumatology and orthopedics. In the context of armed conflicts of recent decades, the nature of military operations is constantly changing and the damaging effects of modern firearms and ammunition are increasing, which is why the treatment of this category of patients requires constant improvement. Traditionally, medical care for the wounded with fractures of long bones of the extremities consisted of timely primary surgical treatment and therapeutic and transport immobilization, which should preferably be performed by extrafocal osteosynthesis using rod external fixation devices (EFD). However, the existing versions and modifications of EFD have different biomechanical and ergonomic characteristics, which, in our opinion, require further revision in order to improve the quality of medical care for the wounded at the stages of medical evacuation. Objective: based on the analysis of biomechanical parameters, assess the stability of external fixation of bone fragments in the constructed loading models “bone – EFD” using various versions of rod EFD using the example of a diaphyseal comminuted fracture of the tibia (type C according to the AO classification). Materials and methods: the material for this study was a 3D printed model of the tibia, built on the basis of CT in the Mimics program. The model took into account spongy and cortical bone tissue. Then, in the SolidWorks automated design system, models of external fixation devices were built, which were then combined with the bone model. Next, a comminuted fracture of the bone diaphysis was formed, type C according to the AO classification. Modeling of the bone – external fixation device system loading was carried out in the Ansys finite element analysis system. Quantitative calculation of the biomechanical characteristics of external fixation was carried out using the finite element method (FE). Results and conclusions: based on the analysis of the biomechanical characteristics, it was revealed that the highest stability indicators for fixing a comminuted fracture are found in the rod external fixation device, the connecting nodes of which were made of titanium alloy. At the same time, the devices, the connecting units of which were made of other materials, demonstrated a sufficient degree of fixation during long loading cycles, without experiencing fatigue damage either in bone tissue or in the elements of the device, which confirms the possibility of using various modifications of rod EFDs in the treatment of comminuted, including gunshot, fractures of the diaphysis of long tubular bones in clinical practice.