Biomechanical study of shaft fracture with the butterfly fragment: software simulation.

The specific traumatic mechanism that leads to the formation of the butterfly fragment is debated in literature. The aim of the present study is to analyze the biomechanics of fractures with a "butterfly" fragment, using a software that simulates the movement of the lines of force (and related iso-displacement points) that occur on the bone, when traumatic forces are applied on it. We have shown that the formation of the butterfly fragment derives from the application of three forces (compression, torsion and bending) with the bending force that acts by increasing the curvature of the long bone.