Wearing analysis for the Schanz screws layout in the cortical section of the tibia with monolateral external fixator

The effect that the layout of the external fixation can have on the dynamic response of the set bone plus fixator and associated relevant implications dealing with the wearing between the bone and the fixator screws has been poorly described. A static analysis of the forces and moments for the fixator-bone mechanical system plus the relative positioning of the screws has been carried out exploring the significance that the centroid of the bone traverse section has as the axial load application point and also a second centroid corresponding to the pairs screw-holes and their inherent distance from it. It has been shown that the stress is significantly larger for the far to centroid screw positioning than that for the close to centroid screw positioning. Simulation results show that the proposed close to centroid screws layout guarantees the reduction of the bone stress at the holes and, as a consequence, the fixator wearing.