Biomechanics of whiplash injury

Abstract

The article reports a new hypothesis of whiplash injury based on a series of experimental studies using isolated human cadaveric specimens. Although the clinical symptoms of whiplash are widely known, the understanding of the underlying injury mechanism is poor. The prevailing view of neck-hyper-extension as the essential injury mechanisms was not supported by recent experiments. In a series of experiments using eight human cadaveric specimens which underwent experimental stepwise whiplash acceleration from 2.5 to 10.5 g functional radiographs and flexibility tests were performed at the end of each acceleration step. Ligament strains, vertebral alignment and elongation of the vertebral artery were monitored during the whiplash trauma by highspeed cinematography and specially designed transducers. After the trauma CT- and MRI-scans were taken and specimens were sectioned using Cryomicrotomy. We found a distinct biphasic kinematic response of the cervical spine to whiplash trauma. In the first phase the spine formed an S-shaped curve with flexion at the upper levels and hyper-extension at the lower levels. This phase was found to be the vulnerable phase of whiplash trauma. The largest dynamic elongation of the capsular ligaments was observed at the C6-C7 level during this initial S-shaped phase of whiplash. The maximum elongation of the vertebral artery could be observed synchronously in the first S-shaped curve of the cervical spine. In the second phase of whiplash all levels of the cervical spine were extended, so that the head reached is maximum extension. No injuries were observed in the second phase. We propose, based on our experimental findings, that with low accelerations the anterior structures of the lower cervical spine are injured during the first phase of whiplash, when the cervical spine forms an S-shaped curve and before the neck is fully extended. At higher trauma accelerations there is also a tendency for the injuries to occur at upper levels of the cervical spine. Based on our findings the traditional view of whiplash as hyper-extension injury can be modified by a differentiated, time dependent, biphasic biomechanical model of the injury, thus allowing better and more effective injury prevention, diagnosis and therapy.

Variability of Morphology and Signal Intensity of Alar Ligaments in Healthy Volunteers Using MR Imaging

“…[31][32][33] Nevertheless, these experiments can only be an approach to reality because the influence of muscular tonicity, for example, cannot be simulated. Results of animal studies in which transient pressure pulses in the cervical spinal canal during experimental neck trauma were recorded indicate that WAD could also appear due to other factors, such as involvement of the cervical spinal nerve root region.…”

In vitro low-speed side collisions cause injury to the lower cervical spine but do not damage alar ligaments

“…Biomechanical data about loads and deformations of the cervical spine during rear-end collisions are available from numerous trials with volunteers [2,3] and some in vitro tests with cadaveric cervical spine specimens [4,7,15,16,25]. Panjabi's in vitro experiment in particular [16] indicated that rear-end collisions might cause functional injury to the lower cervical spine, but not to the upper segments. However, from a clinical point of view, about 20% of all patients suffer from symptoms in the upper cervical spine.…”

Using a Finite Element Model to Evaluate Human Injuries Application to the HUMOS Model in Whiplash Situation

“…In 1971, McKenzie and Williams, 47 using a mathematical model of the head, neck, and torso, predicted that some degree of initial flexion of the head relative to the torso occurs before rapid hyperextension. Later, Grauer et al 48 and Panjabi et al, 49 using cadaveric cervical spines on a benchtop model concluded that in whiplash, the neck forms an S-shaped curvature with lower-level hyperextension and upper level flexion followed by a subsequent C-shaped curvature with extension of the entire cervical spine. In 1999, Kaneoka et al, 50 using healthy volunteers on a sled apparatus, observed that C5-C6 extended before the upper vertebrae in the early phase of whiplash.…”