Seat Belt Fractures

Abstract

Seat belt fractures may be expected more frequently in the future since seat belt installation is now mandatory and public awareness as to the protective value of seat belts is growing. High-speed collisions with the seat belt loose or placed cephalad to the iliac crest bring about this injury (3). The fracture is produced by acute forward flexion of the spine across the resisting belt. With the ligamentous structures remaining intact a horizontal splitting of the vertebrae results. The rent begins in the spinous process or lamina, extending through the pedicles and into the posterior aspect of the vertebral body. The transverse process may be fractured horizontally as well. Compression of the anterior aspect of the body may also be encountered. The constant deformity, however, is the peculiar transverse fracture with posterior separation without dislocation or subluxation. Neurological defects were not encountered in any of the five previously reported cases (1, 2, 3). However, in one of our cases transient numbness and tingling of both lower extremities were followed by persistent weakness in dorsiflexion of the feet. One or more of the upper three lumbar bodies have thus far been the site of involvement. In each of our cases a large hematoma was present over the fracture site which further drew attention to the injury. Seat belt fractures of a lesser extent, for instance those involving only the lamina, pedicle, or spinous process, may be overlooked as we are accustomed to viewing the vastly more common vertebral body compression and vertical fractures of the transverse processes. Treatment consists of immobilization in extension, which reduces the angulation. In one of our cases an H-graft fusion was also employed. Case I: This 21-year-old male was involved in a high-speed collision with a large tree. He was in the back seat of a sedan with the seat belt in use. Looseness of the belt was denied. The abdominal bruises produced by the seat belt were cephalad to the iliac crest. A hematoma was present posterior to the L-2 body. The vertebra was fractured just above the spinous process with the fracture traversing the pedicle and entering the posterior and inferior aspects of the vertebral body with the transverse process also fractured horizontally. A horizontal rent was also present in the spinous process of the L-1 body. The lamina was not entered. No neurological defects were present. Fixation and extension were delayed for one week. This delay resulted in a mild gibbous deformity at the L-2 level. Case II: The 20-year-old brother of the above patient was involved in the same accident and seated on the same seat. Here again, looseness of the seat belt was denied. The bruises were above the level of the iliac crest. A similar, obvious hematoma was present over the fracture site. The spinous process, pedicles, and transverse processes of L-1 were fractured horizontally.