Kinematics of cervical spine injury. A functional radiological hypothesis.

This paper, based on functional radiological knowledge of normal cervical spine kinematics, develops the hypothesis that compressive vertebral injury can be produced by abrupt reversal of curve between hyperflexed and hyperextended parts of the cervical spine. Reversal of curve occurs when the main vector of a compressive force passes between two centers of flexion-extension motion. The hypothesis more clearly explains reverse dislocation of fractured vertebrae than the current concept of Whitley and Forsyth of motion of the head through an arc. The mechanism of injuries with characteristics of hyperflexion of one segment and hyperextension of an adjacent segment, e.g., in certain types of hangman's fractures, is better understood. The hypothesis is expected to be helpful in guiding experimental cervical spine injury, as it relates direction of force to level and type of the resulting vertebral injury.