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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 85
PROCEEDINGS OF THE FIFTEENTH UK CONFERENCE OF THE ASSOCIATION OF COMPUTATIONAL MECHANICS IN ENGINEERING
Edited by: B.H.V. Topping
Paper 6

Computational Modelling in Spinal Biomechanics: A Combined Multi-Body Dynamics / Finite Element Approach

V. Esat1 and M. Acar2

1Department of Computer Science / Research School of Informatics
2School of Mechanical and Manufacturing Engineering
Loughborough University, Leicestershire, United Kingdom

Full Bibliographic Reference for this paper
V. Esat, M. Acar, "Computational Modelling in Spinal Biomechanics: A Combined Multi-Body Dynamics / Finite Element Approach", in B.H.V. Topping, (Editor), "Proceedings of the Fifteenth UK Conference of the Association of Computational Mechanics in Engineering", Civil-Comp Press, Stirlingshire, UK, Paper 6, 2007. doi:10.4203/ccp.85.6
Keywords: spine, multi-body modelling, FE modelling, impact, intervertebral disc, injury prevention.

Summary
Developing computational models of the human spine have been gathering utmost attention in biomechanical research for a couple of decades not only to have a better understanding of the behaviour of the whole spine and the individual spinal parts under various loading conditions, but also to gain an insight for the common injuries it is subjected to and to utilise these models in various design and improvement efforts for injury prevention.

Various models have been developed to investigate situations such as automobile impacts. This study involves the use of two separate computational models in the form of a MB model and an FE model combined with a novel approach. This approach leads to a better understanding of the gross kinetics and kinematics of the human spine, by utilising the predictions of the multi-body model under dynamic impact loading conditions, such as reaction forces at cervical motion segments, as the boundary conditions for the finite element model of the selected cervical intervertebral disc.

In the 3-D multi-body model, the vertebrae have been modelled as rigid bodies, interconnected by linear viscoelastic intervertebral disc elements, nonlinear viscoelastic ligaments and contractile muscle elements possessing both passive and active behaviour. The multi-body model has been built in the same manner as the cervical spine multi-body model of van Lopik and Acar [1]. The validation of the multi-body model has been carried out rigorously. In 15g frontal and 7g lateral impact cases, the model has been validated against NBDL data [2]. As the second model, the detailed biofidelic 3-D non-linear viscoelastic FE model of the cervical C2-C3 intervertebral disc has been developed, reflecting the most characteristic anatomical dimensions of the disc, which helps to realistically analyse the effect of varying loading conditions. Validation has been conducted by comparing the predictions of the model with experimental data. The novel approach has then been used to combine both techniques. The predicted results of maximum von Mises stresses in the annulus and in the whole disc for frontal and rear-end impact cases are presented.

The novel approach adapted has proved to provide a versatile, cost effective and powerful computational tool to analyse the behaviour of the spine under various loading conditions, which in turn help to develop a better understanding of injury mechanisms and to generate guidelines for vehicular and industrial safety and design. This study shows that investigating the biomechanics of the whole human spine and its components and the mechanical response of the intervertebral discs under complex dynamic loading histories is possible and feasible through computational modelling.

References
1
D.W. van Lopik, M. Acar, "The Development of a Multibody Head-Neck System for Impact Dynamics Using visualNastran 4D", Proceedings of ESDA2002, 2002.
2
J. Wismans, E. Van Oorshot, H.J. Woltring, "Omni-directional human head-neck response", 30th Stapp Car Crash Proceedings, Society of Automotive Engineers, SAE Paper No. 861893, 313-331, 1986.

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