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Biofidelity Evaluation of Thoracolumbar Spine Model in THUMS

Henok Afewerki
Göteborg : Chalmers tekniska högskola, 2016. Diploma work - Department of Applied Mechanics, Chalmers University of Technology, Göteborg, Sweden, ISSN 1652-8557; 2016:54, 2016.
[Examensarbete på avancerad nivå]

Thoracolumbar spine injuries in motor vehicle crashes are occurring and the mechanisms are poorly understood. It has been hypothesized to be connected to vehicle’s restraint systems but further studies are required to understand and subsequently address the problem in future restraint systems. Finite Element (FE)-Human body models are invaluable tools for crash analysis, however, quality of the response depends on the biofidelity of the model. The objective of this thesis is to evaluate biofidelity of the thoracolumbar spine model in Total Human Model for Safety (THUMS), Toyota Motor Corporation and Toyota Central R&D Labs . In this thesis work three dynamic and one static thoracolumbar experiments were simulated. THUMS’ ligaments were verified against cadaveric data. Two modified disc material models were inserted in to THUMS and the results compared against experimental data. The Global Human Body Model Concertium model (GHBMC), GHMBC, LLC was also evaluated against cadaveric data from two experiments. All simulations were run in LS-DYNA and pre and postprocessing tasks were performed in LS-PrePost and Matlab. The response of the lumbar FSUs in THUMS’ under the dynamic compression test was similar to the experimental data but was three to four times less stiff. On the other hand, the T12-L5 segment showed fair correlation of reaction force whereas reaction moment was significantly lower. Kinematics of the cadaveric spine under flexion and extension tests was not captured. Reaction moment, shear force and vertical displacement were found to deviate from the response of the cadaveric specimens during the dynamic flexion and shear test. Only horizontal displacement showed good correlation in this test. THUMS performance was good in the static flexion and shear test but poor in flexion only test. Furthermore, the Capsular Ligaments (CL) and the Ligamentum Flavum (LF) in THUMS were found to be about three times shorter and stiffer, respectively. In all the simulations the intervertebral contacts were responsible for the sudden and large increase and vibrations occurring at about the experimental failure point. The modified disc material models improved response of only the lumbar FSUs under the compression test. In conclusion, biofidelity of the thoracolumbar spine model in THUMS is found to be poor and remodelling is necessary. The compliant nature of the intervertebral discs, the shorter length of the CL and higher stiffness of the LF and the smaller initial invetervertebral gap were identified as the main weaknesses of the model.

Nyckelord: Thoracolumbar, Biofideltiy, Kinematics, Flexion, Extension, Shear, Stiffness

Publikationen registrerades 2016-07-06. Den ändrades senast 2016-07-07

CPL ID: 239080

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