Cervical spine biomechanics: a review of the literature.

This article reviews the many clinical and laboratory investigative research reports on the frequency, causes, and biomechanics of human cervical spine impact injuries and tolerances. Neck injury mechanisms have been hypothesized from clinically observed cervical spine injuries without laboratory verification. However, many of the laboratory experiments used static loading techniques of cervical spine segments. Only recently have dynamic impact studies been conducted. Results indicate that crown-of-head impacts can routinely produce compression of the neck with extension or flexion motion. However, the two-dimensional (midsagittal) movement of the head bowing into the chest does not routinely produce flexion/compression type damage to the cervical spine. Flexion/compression damage to the cervical spine can be produced by prepositioning the subject so that upon impact, a three-dimensional motion of the head and neck occurs. Future laboratory research is needed to determine the forces and impact directions required to produce the various known fracture types and dislocations for a clear, accurate description of the cervical spine impact dynamics.