Patterns and mechanisms of lumbar injuries associated with lap seat belts

Of twenty-four lumbar-spine fractures observed in seat-belt wearers, twenty showed an Unusual and consistent pattern of injury characterized by separation of the posterior elements without the usually expected decrease in height of the anterior portion of the vertebral bodies. It is suggested that tension stress is primarily responsible for the unusual patterns seen in these injuries. A mechanism by which large tension forces may be brought to bear on the lumbar spine has been described. Although the lap seat belt is instrumental in producing the lesion described, this report is in no way an indictment of the lap-type seat belt. All of the lesions studied were products of very severe collisions. We are convinced that if these individuals had not been wearing seat belts, they would not have survived. It is likely that these injuries might not have occurred if the patients had been wearing shoulder-type seat belts. The possibility that the shoulder harness might focus similar stress at the cervicothoracic junction with production of a far more serious spine injury remains a matter of conjecture.