BIOMECHANICAL STUDY OF A COMBINED FIXATION SYSTEM FOR GUNSHOT FEMORAL FRACTURES

Abstract

Gunshot injuries of the femur in combat settings are associated with high-energy trauma and unstable diaphyseal fractures (81.4 %), which require fixation methods with increased demands for mechanical rigidity. Objective. To investigate the stress-strain state of a computer model of the femur with a comminuted fracture fixed with an intramedullary spacer and an external fixation device using pins of 5 mm and 6 mm in diameter. Methods. A three-dimensional model of a diaphyseal comminuted femoral fracture and two models of combined fixation («external fixator + intramedullary spacer») with four pins of 5 mm and 6 mm diameter were created. Biomechanical analysis was performed using the finite element method. The evaluated parameters included displacement, stress, and strain under a static load of 400 N. Results. Numerical analysis of the stressstrain state demonstrated that both studied constructs with 5-mm and 6-mm pins provide sufficient fixation stiffness. Increasing the pin diameter to 6 mm resulted in reduced maximal displacements and peak stresses, indicating a biomechanical advantage of the «bone – intramedullary spacer + external fixator with 6-mm pins» system. Conclusions. The conducted numerical stress-strain analysis showed that despite adequate stability provided by both fixation systems, the «bone + intramedullary spacer + external fixator with 6-mm pins» construct has a biomechanical advantage over the construct with 5-mm pins in terms of maximal displacement, stress, and strain values.