Abstract
Motor vehicle accidents frequently cause injuries to the spine resulting in long term disability. The mechanisms of injury however, are poorly understood. Many of the currently available crash test dummies (e.g. EuroSid and Hybrid III) are deficient in consideration of the spine, lacking the correct biofidelic behaviour to accurately predict injury. We have developed a detailed mathematical model of the spine for the investigation of spinal kinematics and injury sustained during passenger vehicle impacts.
The model uses finite element analysis. Surface geometry was reconstructed using digitised co-ordinates from 6 vertebrae (T10 to L3) The location, geometry and physical properties of all 6 ligaments and the intervertebral discs were added. The model was extrapolated to represent the thoracolumbar spine. An independently developed model of the cervical spine was added. The LS-DYNA finite element analysis code was used for simulation of a wide range of non-linear dynamic scenarios. Simplifications of the model included replacement of deformable materials with rigid materials, replacement of complex joints with non-linear springs, and substitution of detailed ligament representations with springs and dampers. The complete spine model was then embedded into a dummy model (Hybrid III) to generate a realistic ‘crash loading’ on the spine.
The model has been validated against published data on stiffness, strength, range of motion, and known physical properties of individual functional spinal units. Further validation has been provided by data from volunteer and cadaveric testing. Loads representing a typical frontal impact were applied to the model. Ligamentous injury was predicted by monitoring forces and deflection within the model. The model accurately predicts bone stresses at which compressive wedge fractures, fractures of the pedicle and neural arch are known to occur.
A validated finite element model comprising 20,000 elements has been developed for analysis of spinal injury. The model accurately predicts ligamentous and bony failure. We hope the model will provide the basis for the development of casualty reducing design strategies within the automotive industry.
The abstracts were prepared by Mr Simon Donell. Correspondence should be addressed to him at the Department of Orthopaedics, Norfolk & Norwich Hospital, Level 4, Centre Block, Colney Lane, Norwich NR4 7UY, United Kingdom.
