Three-dimensional finite element modelling of a dog skull for the simulation of initial orthopaedic displacements.

From 55 frontal tomograms (CT-scans) using the 'Patran' finite element processor, a three-dimensional finite element model (FEM) of a dog skull was constructed. The model was used to calculate bone displacements under orthopaedic loads. This required good representation of the complex anatomy of the skull. Five different entities were distinguished: cortical and cancellous bone, teeth, acrylic and sutures. The first model consisted of 3007 elements and 5323 nodes, including three sutures, and the second model 3579 elements and 6859 nodes, including 18 sutures. Prior to construction of the FEM, an in vivo study was undertaken using the same dog. The initial orthopaedic displacements of the maxilla were measured using laser speckle interferometry. Under the same loading conditions, using the second FEM, bone displacements of the maxilla were calculated and the results were compared with the in vivo measurements. Compared with the initial displacement measured in vivo, the value of the constructed FEM to simulate the orthopaedic effect of extra-oral force application was high for cervical traction and acceptable for anterior traction.