Officially, a seat belt sign consists of contusions and abrasions on the abdomen of a restrained occupant involved in a motor vehicle crash. The seat belt syndrome takes this one step further, with injury to the abdominal organs or spine.
Seat belts save lives by reducing the number of people dying from head injury after a car crash. However, they do so by diverting energy from the head to the chest and abdomen. Overall, people who don’t wear seat belts have a 10% chance of abdominal injury. With seat belts in place, this increases to 15%. And if the person is wearing seat belts and has a seat belt sign, the risk of injury increases to 65%!
This isn’t a bad thing, however. We can fix abdominal injuries, but we can’t fix the brain; it has to heal on its own, and slowly at that.
Seat belts are associated with the Chance fracture, an uncommon fracture of the lumbar spine, usually at L1. These usually only occur with the use of lap belts without shoulder restraints, which is found less and less in cars today. These used to be located in the center of the rear seat, but most new cars offer shoulder restraints in this location now.
Chance fractures need to be assessed by a spine surgeon so that stability can be determined. If stable and there is minimal kyphosis, a brace may be appropriate for treatment. However, if the fracture is not stable or there is more than about 15 degrees of angulation, surgery will be necessary.
As seat belt use increases, seat belt signs are becoming more common. Any patient with a seat belt sign must have an abdominal CT. If any abnormal findings are noted, a surgeon must be consulted because it is very likely that operative intervention will be required.