Neck Injury Criteria Tolerance Levels

The neck injury criteria are comprised of five different injury criterion:

• Neck Upper Tensile Load. (KN)
• Neck Upper Compressive Load. (KN)
• Neck Upper Longitudinal shear force (same for fore and aft loads). (KN)
• Neck Upper Longitudinal extension bending moment. (Nm)
• Neck Upper Longitudinal flexion bending moment. (Nm)

The problem in defining the four tolerance levels, between the 5 injury levels, for each of the above criterion is that each has a different baseline tolerance ranging from no injury to an AIS 4.  Appendix 1, Table 21 shows the levels currently used in occupant protection standards with the relative AIS for loads at the upper cervical spine.  The other major problem with predicting neck injuries is that there is not a gradual increase in injury as the loading rises.  At a specific combination of loads, which will vary considerably in the population, a particular injury will occur, with potentially fatal consequences.  So below this tolerance level the victim will have no injury but above a potentially fatal one.

These have been used to produce the upper cervical spine tolerance levels for the four injury classifications as shown in Appendix 1, Table 22.  Further research work is required to propose tolerance levels for the lower cervical spine.