Figure 12.5 Schematic of the trauma shown in Figures 12.2 and 12.3. The spine starts in a neutral position (NP). The 50 to 75 ms time period illustrates the neck forming an S-shaped curvature (Phase I). During this phase, the lower cervical spine intervertebral joints exhibit hyper-extension, exceeding their physiological limits. In the later phase (Phase II), the spine transforms to a C-shape with complete extension. This phase is associated with a lesser degree of the lower level hyper-extension, and thus a lesser potential for injury.

ABSTRACT

In fact, the above described work did not produce head extensions beyond physiological limits (Grauer et al., 1998). This finding is similar to in vivo findings of two recent studies in which whiplash experiments were conducted with volunteers (Matsushita et al., 1994; McConnell et al., 1993) and suggests that injury could not be caused by simple neck extension. The work of MacNab, as well as that of many other early investigators, may have missed the potentially more damaging Phase I response to whiplash because of an inability to monitor individual intervertebral motions continuously.