Mechanisms of Cervical Spine Injury During Impact to the Protected Head

Static and impact loading of the heads of embalmed cadavers wearing protective helmets have been conducted for the purpose of understanding the mechanics of fracture-dislocation injury to the cervical spine. Some of the cadavers were cut down on one side of the neck for high-speed photographic observation of the spine during impact. Others were instrumented with strain gages on the bodies and near the facets to assist in correlating spine movements and load configuration with strain distribution.

Results indicate that static loading can be a useful predictor of failure site under dynamic conditions. Those conditions which were found to be most influential on injury site and level of strain were: 1) The extent to which the head was gripped by the impact surface to allow or restrict motion at the atlanto-occipital junction; 2) Impact location; and, 3) Impact force alignment with the spine.

It was found that very little could be done with energy-absorbing material in the crown to reduce spine strain due to a crown impact. Also, the rear rim was not a ‘guillotine’ threat to fracture-dislocation from blows which cause hyperextension, and the higher cut rear rim recommended to reduce or eliminate this alleged hazard caused higher strain by virtue of allowing greater extension of the neck.