title: Investigation of factors affecting loosening of Ilizarov ring-wire external fixator systems at the bone-wire interface.
abstract: The potential for peri-implant bone yielding and subsequent loosening of Ilizarov ring-wire external fixation systems was investigated using non-linear finite element (FE) analyses. A strain-based plasticity model was employed to simulate bone yielding. FE models also incorporated contact behavior at the wire-bone interface, orthotropic elasticity, and periosteal-endosteal variation of bone properties. These simulations were used to determine the extent and location of yielding with change in age-related bone structure and properties for the bone-Ilizarov construct at the tibial midshaft. At critical wire-bone interfaces, the predicted volume of yielded bone with four wires (on either side of the fracture) was ∼40% of that with two wires. Old-aged cases showed considerably greater bone yielding at the wire-bone interface than young cases (1.7-2.2 times greater volumes of yielded bone). The volume of yielded bone at all wire-bone interfaces decreased with an increase in wire pre-tension. The absence of continuous through-thickness yielding offers an explanation for the clinical observation that Ilizarov ring-wire fixation can provide stable fracture fixation even in bone with high porosity.
authors: School of Engineering, The University of Edinburgh, Edinburgh, United Kingdom.
authors: Finn E
authors: FE
authors: Donaldson
authors: Pankaj
authors: P
authors: Pankaj
authors: A Hamish R W
authors: AH
authors: Simpson
mesh_terms: D001864:Bone Wires / Q000009:adverse effects*; D004868:Equipment Failure; D016267:External Fixators / Q000009:adverse effects*; D005260:Female; D005592:Fracture Fixation / Q000009:adverse effects*; D006801:Humans