Biomechanical approach to the choice of the type of intramedullary fixator in a simulated femoral fracture

Abstract

Intramedullary osteosynthesis is currently one of the main methods of treating fractures of long tubular bones. There is a large selection of both the fixators themselves and the manufacturers of these implants. The aim of this study was to conduct biomechanical testing of three types of intramedular rods – ChM, BNB (three-bladed), SarNIITO rod and Fixion (Israel) in femoral fractures of types A1, A2, A3 and B1. According to the results of the study of the displacement of fragments in different types of fractures, affecting the “bone– fixator” system with three types of loads (axial, transverse and rotational) – the stability is not the same. The most commonly used cross-blocking rod (or perhaps the entire type of such rods) showed fairly good indicators of the stability of fragments that can lead to the desired result – bone fusion. The use of different types of intramedullary fixators based on a different method of locking in the bone (transversely inserted screws, by expanding in the bone marrow canal, embedding the blades into the bone from the inside and with a spoke) allows a more rational approach to increasing the stability of a fixed fracture by using their positive sides. So, for a fracture of type A1 and A2, it is better to use Fixion rod. With a transverse bone fracture line (type A3), it is better to give preference to the three-bladed BNB rod, since it holds the transverse and rotational load better, and when exposed to the axial one, the fracture is autodynamized (compression), stimulating regeneration. Fractures of type B2 (comminuted, with a small contact line between the fragments) require the maximum possible stability. For this purpose, Fixion rod is better suited, which is blocked throughout the entire bone marrow canal. But when it is used, it is possible for the fragment to move away from the mother bed when the rod is stabilized by its expansion.