FINITE ELEMENT ANALYSIS OF THE TALUS

The talus bone forms the main connection between the leg and the foot. It is therefore subject to large loadings, which are passed down through the leg via the tibia, through the talus and into the foot complex via the calcaneus and navicular bones. These forces give rise to internal stresses within the talus, which may in time lead to deformation and fracture of the bone. The purpose of this study was to analyse these stresses that occur in normal everyday operations, determining their location and value. This was done by developing an accurate Finite Element (FE) model of the talus, which could then be constrained in the appropriate contact areas and have a load applied to it as exerted by the tibia.
A three-dimensional model was created by measurement of a casting using a Co-ordinate Measuring Machine. This data was then imported into the FE package and the model produced. Appropriate material properties were assigned to the model to simulate the physical make up of the actual bone. The model was then prevented from deforming in physically impossible ways by constraining its surfaces where required. A suitable element mesh was then generated and a load applied to the tibial articulating surface that would simulate a normal standing load.
The analysis was then performed and the results obtained, indicating the locations of high stress and their magnitude. It was found that the maximum von Mises stress reached a value of 10.4 MegaPascals, and was located in the lateral neck area. This correlates with clinical findings, where the neck region is a common failure site when fractures of the talus occur.