A Chance
fracture refers to the type of spinal fracture that can occur when
there is acute hyperflexion of the back. First described by G.Q.
Chance in 1948, this fracture involves a horizontal splitting of the
vertebra that begins with the spinous process or lamina and extends
anteriorly through the pedicles and vertebral body. The vertebral
body tends to have a wedge compression fracture and the posterior
elements of the vertebra are distracted. Despite the extent of
damage to the vertebra these fractures tent to be stable fractures.
These fractures most commonly occur at the T12, L1, or L2 level,
also known as the thoracolumbar spine. This is the junction of the
relatively rigid thoracic spine and the more flexible lumbar spine.
After G.Q. Chance’s original description in 1948, Chance fractures
later became known as "seat-belt" fractures with the advent of lap
seat belts in cars. A head-on collision would cause the passenger
wearing a lap-belt to suddenly be flexed at the waist, thus creating
tremendous stress on the posterior elements of the vertebra.
Starting in the 80’s and 90’s the combination of shoulder and lap
belts were installed in automobiles. After this switch Chance
fractures have become less associated with automobile injuries. Most
Chance fractures seen in today’s emergency rooms result from falls
or crush type injuries where the thorax is acutely hyperflexed.
The incidence of associated intraabdominal injuries with a Chance
fracture reaches 50%. Therefore, when a Chance fracture is diagnosed
a CT of the abdomen should be obtained. Injures associated with
Chance fractures include fractures of the pancreas, duodenum and
mesentery contusions or rupture.
Radiologic Overview of the Diagnosis:
The AP view of the spine may reveal disruptions of the pedicles
and loss of vertebral body height. Frequently a transverse process
fracture will be identified on the AP projection. The lateral view
will demonstrate the spinous process fracture and fractures through
the laminae and pedicles. The vertebral body will usually look
compressed and wedge shaped.
CT of the spine should be performed on all Chance fractures to
assess the extent of the fracture and to evaluate the spinal canal.
Sagittal reconstructions of the axial images provide a great deal of
information about the fracture pattern.
- Posterior element fractures are better seen on the lateral
projection; however the AP view helps to demonstrate pedicle
involvement.
- CT of the spine with sagittal reconstructions should be
performed on all Chance fractures
- CT of the abdomen should be obtained due to the 50% risk of
significant intraabdominal injury.
