Three-Dimensional Modelling and Finite Element Analysis of an Ankle External Fixator

The use of ankle external fixator to treat pilon fracture Type III is popular amongst surgeons as it can reduce complications such as non-union and mal-union. Even though configurations of the connecting bars are important, the material also plays a major factor for a successful outcome. In this paper, the Delta external fixator with simulated ankle pilon fractures Type III were modelled and analysed under two different materials; titanium alloy and stainless steel. The finite element model includes tibia, fibula, talus, calcaneus, cuboid, navicular, three cuneiforms and five metatarsals bone. To simulate the pilon fractures Type III, a cutting segment was utilised. The ligaments were assigned with linear spring properties and cartilages were modelled using Mooney-Rivlin hyper-elastic behaviour. The Delta external fixator was designed using a three-dimensional software with two different material properties - titanium alloy and stainless steel. High von Mises stress concentrated at the pin-bone interface with the highest value observed for the titanium fixation. The results also showed less deformation for the stainless steel compared to titanium.