Factors related to quadriplegia in football and the implications for intervention strategies.

Axial compressive loading, the principal cause of spinal cord quadriplegia in American football, is produced when a player is forcibly struck on the crown of the helmet. This impact subjects the small cervical vertebrae to a large compressive force that often produces stress that exceeds the failure limit of the spine. Several factors influence the outcome in axial collisions, including the available kinetic energy, the displacement needed to dissipate the energy, and the end conditions of the collision (i.e., the position of the head). Effective intervention of this catastrophic injury requires the melding of information from the fields of biomechanics and epidemiology. From a biomechanical perspective, neck loading should be kept at a level that is below the failure limit of the cervical spine. The epidemiologic rate at which these injuries develop among football players suggests that cervical quadriplegia is rare. Thus, protective devices intended to lower the forces on the cervical spine may not succeed in dramatically reducing the incidence of this injury. Because this injury is rare, it is important to consider that introducing new protective equipment, intended for intervention of one problem (i.e., cervical quadriplegia), may lead to other injuries.