Abstract
Purpose of the study
The aim of this mechanical study was to investigate the ability of cannulated fixation bolts to stop wire slippage in Ilizarov circular external fixators.
Methods and Results
Three types of cannulated fixation bolts (Smith and Nephew, Orthofix and one designed by the authors) were tested on Ilizarov rings to compare their performance. Three levels of bolt torques were applied and the wires were pulled to measure the load at which the wire will start to slip or fail. It was revealed that the initial resistance to slippage is due to plastic deformation of the wire under the clamp and is in fact governed by the size of this deformation. The slippage was found to occur in a slip/stick fashion, as the plastic deformation was propagated along the wire.
Conclusion
The more the plastic deformation caused by the bolt on the wire the higher the initial resistance to loading.
