Pediatric lumbar Chance fractures in British Columbia: chart review and analysis of the use of shoulder restraints in MVAs

Chance fractures of the skeletally immature spine classically occur in frontal motor vehicle accidents (MVAs) when the occupants are restrained by a lap belt only and undergo traumatic hyperflexion of the torso during the impact. We retrospectively examined all MVA-related Chance fractures at British Columbia's Children's Hospital since 1986, by collecting injury and seat-belt use information from chart data and imaging studies. Twenty-six patients were included in the study, 14 wore a lap belt only, seven wore a three-point restraint properly, and five were reportedly misusing the shoulder portion of a three-point restraint. The subjects ranged in age from 3 to 16 with a mean age of 10.6 years. Eleven of the 26 (42%) patients sustained abdominal viscera injuries, seven of the 26 patients suffered neurologic injury (spinal cord and/or spinal nerve injury) associated with their spinal fracture, with two cases of complete paralysis, and there was a 38% incidence of head injury. Concomitant injuries (i.e. to the head, abdomen and abdominal contents) tended to be mitigated by the presence of a properly worn shoulder restraint. This leads to the conclusion that Chance fractures can be sustained even when the occupant is using a shoulder belt to restrain their torso. The mechanism responsible for this is unknown. This may indicate that Chance fractures can be caused by a lesser degree of torso hyperflexion than previously thought. Alternatively, we also speculate that Chance fractures can occur while the torso is restrained by the shoulder belt if the hips submarine beneath the lap belt and the torso experiences hyperflexion secondary to forward excursion of the pelvis and legs during the collision. Future work is necessary to confirm these mechanisms and to find ways to prevent them. These studies will need to use computational or experimental child surrogates that can sit in a slouched posture and submarine during a collision.