A simple way to model wires used in ring fixators: analysis of the wire stiffness effect on overall fixator stiffness

The Ilizarov fixator has become widely used in the treatment of complex trauma and deformity correction in the United Kingdom over the last few decades. As such, it has been widely researched. Within this fixator, the characteristic fine wires are the weakest and most flexible component. The wires allow interfragmentary micromotion, which is believed to be beneficial to bone healing. In this paper, a novel and simple numerical model of the stiffness and deflection of the wires when the fixator is subject to axial and torsional loading is presented. A range of wire lengths and pretensions are analysed, and the results compared to the findings of other researchers, with generally good agreement. This indicates that fixator stiffness can be determined simply and without recourse to sophisticated finite element analyses or extensive physical testing. In addition, the model is used to predict the contribution of the wires to the overall stiffness of the fixator.