Two- and three-point seat belt restraints have reduced mortality and the severity of trauma due to motor vehicle crashes; however, they occasionally produce injury. Lap/shoulder belts are known to produce abdominal (most common), thoracic, and spinal injuries. The “seat belt sign,” abrasions or ecchymoses to the neck, chest, and abdomen in the pattern of the belt, occurs in less than 20% of patients but is associated with a fourfold risk of intrathoracic and an eightfold risk of intra-abdominal injury.
Seat Belt Injury. Ecchymosis from the lap belt is evident. A subtle Destot’s sign, which is inguinal or perineal ecchymosis, in a patient with a pelvis fracture. (Photo contributor: R. Jason Thurman, MD.)
Seat Belt Injury. Abrasions from a three-point restraint causing rib fractures and a pneumothorax. (Photo contributor: Brad Russell, MD.)
Management and Disposition
Patients with seat belt ecchymosis should undergo contrast-enhanced CT of the chest, abdomen, pelvis, and thoracic and lumbar spine due the increased probability of injury. Alternatively, hospital admission with serial examinations and laboratory studies (CBC, hepatic panel, lipase, urinalysis) is a reasonable management option.
Up to 36% of patients with a seat belt sign have an abdominal injury requiring laparotomy.
Lap belt–only passengers are more likely to have a Chance fracture and small bowel injury if they have an abdominal seat belt abrasion after a motor vehicle crash.
Seat Belt Injury. Neck abrasions from a three-point restraint in a patient involved in a head-on motor vehicle crash. (Photo contributor: David Effron, MD.)
Chance Fracture. T-12 Chance fracture in a restrained passenger involved in a head-on motor vehicle crash. (Photo contributor: Lawrence B. Stack, MD.)