Acceleration injury of the cervical spine by hypertranslation of the head. Part I. Effect of normal translation of the head on cervical spine motion: a radiological study.

This paper starts from the concept that acceleration injury of the cervical spine is caused by hypertranslation of the head with respect to the trunk, and not by hyperflexion or hyperextension. This first part of the paper studies the effect of normal head translation upon cervical spine posture and motion. Lateral radiographs of the neck in chin-out and chin-in positions reveal that this translation produces maximal motion at the cranio-vertebral junction C0-2, from full extension in chin-out position to full flexion in chin-in position. Motion decreases from C2-3 downward. Below C6 the direction of motion is reversed. The normal range of head translation is small, notably with a fixed thoracic spine. The hypothesis is developed that hypertranslation of the head will almost immediately result in damaging hyperflexion or hyperextension of the craniovertebral junction.