The Mechanism of Injury to the Spinal Cord in the Neck without Damage to the Vertebral

The discrepancy between damage to the spinal cord and to the vertebral column in cervical injuries has been the subject of comment by many authors. Both cord damage without vertebral column injury, and vertebral fracture and dislocation without cord dysfunction, are recognised. This communication concerns the former group. The commonly observed anatomical displacement in skeletal injuries of the cervical spine is fracture-dislocation in hyperflexion, and it is caused by hyperfiexion. Not unnaturally it was supposed that spinal cord damage without persistent vertebral displacement was caused during acute hyperfiexion , involving temporary dislocation , immediately reduced spontaneously by muscular action. This hypothetical series of events was designated ‘ ‘ recoil injury of the cervical spine. ‘ ‘ The improbability of this explanation ‘as demonstrated by Cramer and McGowan (1944). They suggested temporary intraspinal displacement of an intervertebral disc as the explanation, and postulated acute forcible flexion of the neck as the cause of the supposed temporary disc displacement. As evidence, they relied upon the occasional findings of a prolapsed cervical disc as a cause of cord compression after injury, but they did not adduce proof that a temporary prolapse can occur, nor that it could account for spinal cord contusion. Barnes (1948) showed that hyperfiexion can cause cord compression only if it is sufficient to dislocate and lock the articular processes. Locking of this type is not susceptible of spontaneous reduction. As was pointed out by Taylor and Blackwood (1948), injuries causing cervical cord damage in the absence of vertebral fracture or dislocation are usually sustained by forcible extension of the neck rather than by hyperfiexion. Such accidents are exemplified by diving with the head back into shallow water, by falling forwards downstairs or by being thrown forwards while the head is arrested by a fixed object, as in motoring accidents. Taylor and Blackwood described a case in which rupture of the anterior longitudinal ligament and temporary dislocation in hyperextension occurred, leaving no trace detectable by radiography. They suggested that this might be a relatively common occurrence and might explain many of the cases in question. Subsequent observations, however, indicate that a simpler mechanism is probably the common cause of damage to the cord. The findings suggest that the injury is caused by hyperextension of the cervical spine without temporary dislocation, and that the agent which impinges on the cord is the forward-bulging ligamentum flavum.