Biomechanics of the cervical spine Part 3: minor injuries.

Minor injuries of the cervical spine are essentially defined as injuries that do not involve a fracture. Archetypical of minor cervical injury is the whiplash injury. Among other reasons, neck pain after whiplash has been controversial because critics do not credit that an injury to the neck can occur in a whiplash accident. In pursuit of the injury mechanism, bioengineers have used mathematical modelling, cadaver studies, and human volunteers to study the kinematics of the neck under the conditions of whiplash. Particularly illuminating have been cinephotographic and cineradiographic studies of cadavers and of normal volunteers. They demonstrate that externally, the head and neck do not exceed normal physiological limits. However, the cervical spine undergoes a sigmoid deformation very early after impact. During this deformation, lower cervical segments undergo posterior rotation around an abnormally high axis of rotation, resulting in abnormal separation of the anterior elements of the cervical spine, and impaction of the zygapophysial joints. The demonstration of a mechanism for injury of the zygapophysial joints complements postmortem studies that reveal lesions in these joints, and clinical studies that have demonstrated that zygapophysial joint pain is the single most common basis for chronic neck pain after injury.