Biomechanics of the cervical spine Part 3. minor injuries

Minor injuries of the cervical spine are essentially defined as injuries th at do not involve a fracture. Archetypical of minor cervical injury is the whiplash injury. Among other reasons, neck pain after whiplash has been con troversial because critics do not credit that an injury to the neck can occ ur 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. Particu larly 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 cerv ical 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 t he anterior elements of the cervical spine, and impaction of the zygapophys ial joints. The demonstration of a mechanism for injury of the zygapophysia l 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. (C) 20 01 Elsevier Science Ltd. All rights reserved.