Biomechanics of the cervical spine. I: Normal kinematics

This review constitutes the first of four reviews that systematically addre ss contemporary knowledge about the mechanical behavior of the cervical ver tebrae and the soft-tissues of the cervical spine, under normal conditions and under conditions that result in minor or major injuries. This first rev iew considers the normal kinematics of the cervical spine, which predicates the appreciation of the biomechanics of cervical spine injury. It summariz es the cardinal anatomical features of the cervical spine that determine ho w the cervical vertebrae and their joints behave. The results are collated of multiple studies that have measured the range of motion of individual jo ints of the cervical spine. However, modern studies are highlighted that re veal that, even under normal conditions, range of motion is not consistent either in time or according to the direction of motion. As well, detailed s tudies are summarized that reveal the order of movement of individual verte brae as the cervical spine flexes or extends. The review concludes with an account of the location of instantaneous centres of rotation and their biol ogical basis. (C) 2000 Elsevier Science Ltd. All rights reserved.