Chance fractures also referred to as seatbelt fractures, are flexion-distraction type injuries of the spine that extend to involve all three spinal columns. These are unstable injuries and have a high association with intra-abdominal injuries.

Chance fracture is also known as the "seatbelt fracture". The fracture typically occurs where the fulcrum is the seatbelt and the point of motion is the spine itself. Therefore, the spine tears apart in a horizontal fracture into the upper and lower parts. Thus, the anterior and middle columns fail in compression (moving together or in "flexion"), and the posterior column fails in distraction (moving apart). Bones often fracture before the ligaments because the ligaments have higher tensile strength than the bones ¹.

Location

This fracture most commonly occurs about the upper lumbar spine (with the thoracolumbar junction accounting for ~50% of cases ³), but it may be observed in the mid lumbar region in children.

Associations

There is a high incidence of associated intra-abdominal injuries (especially the pancreas and duodenum) that can result in increased morbidity and mortality. Associated intra-abdominal injuries appear to be more common in the pediatric age group with an incidence approaching 50%.

If unrecognised, Chance injuries may result in progressive kyphosis with resulting pain and deformity.

Radiographic features

Anterior wedge fracture of the vertebral body with a horizontal fracture through posterior elements or distraction of facet joints and spinous processes.

Plain radiograph

empty vertebral body sign: can be seen on an AP radiograph and results from the vertical separation of the posterior elements displacing the spinous processes or spinous process fracture fragments of the vertebral body on the AP projection
transverse fractures across the transverse processes, laminae, and articular processes
widening of the interpedicular distance: often suggests a burst component
widening of the facet joints and increased intercostal spacing
widening of the interspinous spaces

CT

more accurately delineates fracture details

MRI

useful to assess for ligamentous injury and cord injury

Treatment and prognosis

Treatment is broadly classified into non-surgical management with a stabilizing brace or orthotic or surgical management, usually by posterior fusion +/- anterior fusion.

Non-surgical management may be suitable for patients with no neurological defects and stable posterior elements ⁵. It should be noted that patients managed non-operatively need long term follow-up to ensure they do not develop any kyphotic deformity.

Patients with any neurological deficit or unstable fracture patterns (damage to the posterior ligaments) will need surgical fixation to decompress the spinal cord and stabilize the fracture ⁵. If immobilization is impractical (large body habitus) or the patient has polytrauma, surgical management may also be indicated.