[Biomechanical aspects of injuries of the cervical vertebrae].

A biomechanical expert opinion on the injury mechanism is necessary only in a few cases. However, the judgement of these cases is extremely compromised if the mechanics of injury are described incorrectly in the clinical report. Since the mechanism of neck injuries is very complex, the physician without biomechanical training should concentrate on the familiar clinical findings; The relevant mechanisms of indirect neck trauma are (a) a non-head-contact mechanism (hyperflexion or hyperextension, hypertranslation, acceleration) and (b) head contact leading to compression, hyperflexion, hyperextension and/or hypertranslation. A non-head-contact mechanism occurs, for example, in the case of rear end impact without head restraint (hyperextension) or a frontal collision involving a belted occupant (hyperflexion), without head impact. The term "whiplash" is misleading and incorrect: It presumes a virtually non-existent two-phase movement back and forth (or vice versa), and it confuses the physical criterion mechanism and the anatomical or morphological criterion injury, e.g. distortion, sprain etc. A head-contact mechanism involves momentum exerted from the head on the neck. Again, the anatomical and morphological terms are the same, but the mechanism is different. With a contact mechanism and a non-contact mechanism, not only a hyperflexion or a hyperextension can occur; in the first phase of the impact, a shearing force between the upper vertebral bodies (C0-C2) may load the intervertebral structures by hypertranslation.