Abstract
There is a large body of work investigating whiplash-associated injury in motor vehicles
and its causation. Being unable to detect the actual injury and having to use the
symptoms of the sufferer as a surrogate has made progress in understanding the injury
causation slow. Still lacking are the causal relationships between the biomechanical load
on the vehicle occupant in the crash, the resulting loading on the neck and the actual
injuries suffered. The optimisation of the design of vehicle safety systems to minimise
whiplash needs a better understanding of human tolerance to these injuries.
This thesis describes the development of a mathematical multi-body C5/C6 motion
segment model to investigate the causation of soft-tissue neck injury. This model was
validated with available static in-vitro experimental data on excised motion-segments
and then integrated into the existing, validated multi-body human head and neck model
developed by van der Horst, to allow the application of realistic dynamic loads. The
responses and injury sensing capability of the C5/C6 model were compared with
available data for volunteers and cadavers in rear impacts.
The head and neck model was applied to the investigation of a group of real rear impact
crashes (n = 78) of vehicles equipped with a crash-pulse recorder and with known postcrash
injury outcomes. The motion of the occupants in these crashes had previously
been reconstructed with a MADYMO BioRID II dummy-in-seat model validated by
sled testing. The occupant T1 accelerations from these reconstructions were used to
drive the head and neck model. The soft-tissue loading at C5/C6 of the head and neck
model was analysed during the early stage of the impact, prior to contact with the head
restraint. The loading and the pain outcome from the vehicle occupants in the actual
crash were compared statistically.
For the longer-term whiplash-associated pain outcomes (of greater than 1 month
duration) for these occupants, the C5/C6 model indicated good correlation with the
magnitude of the shear loading on the facet capsule. In lower severity impacts, the
model result supported a second hypothesis of injury to this motion segment: facet
surface impingement.