Spinal Disc Herniations in Occupants Involved in Frontal Impacts 2018-01-0545
Disc herniations in the spine are commonly associated with degenerative changes, and the prevalence increases with age. Though rare, spinal disc herniations can also be caused by trauma. With increasing number of older drivers on U.S. roads, there is an expected proportionate increase in clinical findings of disc herniations in occupants involved in vehicle impacts. Our goal in this study is to determine whether there is a causal relationship between frontal impacts and the occurrence of disc herniations in the occupants of these impacts. We further aim to determine the prevalence of different types of spinal injury and to evaluate the effects of crash severity and other parameters on different types of spinal injury in such impacts. Using data from the National Automotive Sampling System - Crashworthiness Data System (NASS-CDS) database from 1993 through 2014, we examined the reported occurrence of all spine injuries for adult occupants in frontal impact. The results show that the most common spine injury is an acute muscle strain of the neck, followed by strain of the low back. The delta-V of a frontal impact is a significant predictor of acute cervical strain. The number of occupants with disc herniations was relatively small in the three segments of the spine: 15 occupants with neck disc herniations, 3 in the thoracic spine, and 3 in the lumbar spine for the 34,911 raw cases, in contrast to a background prevalence of 10 to 30% spinal disc herniations in asymptomatic individuals. In light of known neck responses of restrained volunteers and post mortem human subjects (PMHS) during frontal impacts, the low prevalence of neck disc herniations observed in the present study can be explained by an absence of the known experimental mechanism of a combination of axial compression and hyperflexion to produce a traumatic disc herniation. The thoracolumbar spine, on the other hand, experiences compression during a frontal impact, suggestive of a possible mechanical environment to produce a traumatic disc herniation. However, the low prevalence of thoracolumbar disc herniations in the present study can be explained by the fact that vertebral body fractures are more likely to occur under similar conditions because the endplate of the vertebral body is the weaker link. The mechanism to produce compression in the thoracolumbar spine during frontal vehicular impacts is unclear and needs to be further investigated.