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Axial compression of the cervical spine is a significant source of spinal cord trauma and quadriplegia. This paper summarizes a number of studies related to injury mechanisms and potential strategies for reducing the risk of trauma. Head first collisions at 1.8 m.s-1 were conducted with a mechanical test dummy fitted with a force and moment transducer in the neck. Films taken at 500 fps confirmed that the head-neck-torso system was decelerated in stages rather than uniformly, so that the neck became trapped between the fixed head and moving torso. Compression forces were about 4800N for the neutral neck and 3800N for the flexed neck. Further analysis with a post-processing computer model of the cervical spine revealed compressive forces in excess of 5000N in the lower regions (C5, C6, C7) for both the flexed and neutral postures. Simulations with the neck extended suggest that the anterior longitudinal ligament, the neural arches and spinous processes would likely be damaged. When the ATD was subjected to blows that produced side bending of the head and neck the compressive force output from the transducer was 50% lower when compared to direct axial loading. This side bending posture appears to offer some promise in reducing the compressive loads on the spine due to head first collisions.
Axial Loading, Cervical Spine, Impact Postures, Flexed/Extended Neck, Lateral Bending
Professor, University of Waterloo, Waterloo, Ontario