Haptically integrated simulation of a finite element model of thoracolumbar spine combining offline biomechanical response analysis of intervertebral discs

In this paper, we first describe the construction of a finite element model of the human spine that may be used to assist the investigation of clinical problems by predicting its biomechanical behaviour. A beam finite element (FE) spine model for haptic interaction is built based on a solid FE spine model, which is created in an offline finite element analysis (FEA) software. The mechanical properties of the beam FE spine model are tuned so that its deformation behaviour is very similar to that of the offline solid spine model. Furthermore, the online beam FE spine model is greatly simplified as compared to the offline solid FEA model and hence more appropriate for real-time simulations. Haptic feedback is provided in the real-time simulation of the beam FE spine model, in order to enhance the human-computer interaction. Based on the results of spine deformation obtained from the haptic online FE simulator, the offline FEA spine model again is used to reproduce the same deformation and hence to provide more detailed deformation and vertebrae's stress/strain information, which the haptic beam FE model is not capable to provide. Then, we present a tetrahedral mass-spring system to model intervertebral discs, which are interposed between vertebrae, and the offline simulation can be run to achieve deformation responses of these intervertebral discs. In our research, combining the haptic beam FE model and the intervertebral disc model can be useful for studying biokinematics of the spine as well as assessing medical conditions in the spine or the biomechanical behaviour of new designs of artificial intervertebral discs. (C) 2010 Elsevier Ltd. All rights reserved.