A head-on collision would cause the person wearing a lap-belt to suddenly flex his spine at the waist, creating severe stress on the posterior elements of the vertebra. Known as “seat-belt” fractures, chance fractures are flexion distraction injuries that can occur when there is acute hyperflexion of the back. This fracture occurs around a fixed point anterior to the spine. Chance fractures are less associated with motor vehicle accident after shoulder and lap belts were installed. These fractures were probably a result from falls or crush injuries.
There are two kinds of chance fractures:
- Bony Chance
- Ligamentous Chance
Bony injuries could heal with immobilization, casting, or bracing. However, with a ligamentous chance injury, the soft tissues and ligaments do not heal and will require surgery. Chance fractures typically are a three column injury with a horizontal orientation of the fracture. These fractures most commonly occur at the level of T12, L1, or L2, also known as the thoracolumbar spine. This injury is not associated with neurological deficits. The physician will want to obtain a CT scan of the abdomen because this injury is associated with intraabdominal injuries.
