Seat‑belt syndrome
Overview
Seat‑belt syndrome describes a recognisable pattern of injury after a motor‑vehicle collision in which force from a seat belt (most commonly the lap belt) produces a combination of abdominal wall bruising (“seat‑belt sign”), intra‑abdominal visceral injury and thoracolumbar spinal injury. The eponym is a useful prompt to expect occult bowel/mesenteric and flexion-distraction spinal injuries after a belted mechanism, but investigation and management should follow major‑trauma pathways and national imaging guidance (NICE NG39 and NG41).
Mechanism
Rapid deceleration causes the torso to pivot about the lap belt, which acts as a fulcrum. The resulting flexion-distraction and compression forces:
- compress abdominal viscera against the vertebral column, risking hollow‑viscus and mesenteric injury.
- load the thoracolumbar spine, producing flexion-distraction injuries (Chance fractures) or, with axial load, burst fractures.
- injure the anterior and posterior abdominal wall (contusions, degloving, traumatic hernia).
Risk is higher with improper restraint (lap‑belt only, shoulder belt behind the back, poor belt fit in children).
Typical clinical pattern
Classic triad
- Seat‑belt sign: linear abdominal wall ecchymosis or contusion along the belt line.
- Intra‑abdominal visceral injury: small‑bowel perforation, mesenteric tear with devascularisation, retroperitoneal haemorrhage, or solid‑organ laceration.