Flexion Distraction Injury of the Lumbar Spine
It is sometimes called a seat belt injury or “chance
fracture”. Usually, the patient is restrained, back seat passenger that is
involved in a car accident and the person is wearing only a lap seat belt. The
chance fracture is a variant of the flexion/distraction injury. The terminology
is sometimes confusing, but a chance fracture could indicate a bony injury. It
may present itself with a minimal compression fracture of the vertebral body,
however, in this case all three columns of the spine are injured from
distraction and tension. When you deal with a traumatic compression fracture in
a young patient that is involved in a car accident, rule out a seat belt injury
or “chance fracture”. This condition could be misdiagnosed or not diagnosed.
Bowel trauma occurs in these cases due to crushing of the bowel between the lap
seat belt and the spinal column, which results in devascularization and acute
bowel rupture. In flexion/distraction injury, there will be an anterior wedge
fracture of the vertebral body plus horizontal fracture of the posterior
elements or distraction of the facet and the spinous processes. If it goes
unrecognized, it may lead to progressive kyphosis with pain and deformity. This
injury usually occurs in the thoracolumbar junction or in the midlumbar are.
The posterior column fails first because of the axis of rotation is anterior to
the vertebral body. The flexion/distraction injury is unstable in flexion and
usually needs surgery to restore the disrupted tension band and prevent
progressive deficit and pain, as well as enhance the functional recovery of the
patient. In patients with flexion/distraction injury of the lumbar spine, up to
50% of these patients have associated potential life threatening injures such
as visceral and gastrointestinal injury. Look for transabdominal ecchymosis;
you will probably need to consult a general surgeon, and this condition occurs
more in children. The hallmark of this injury is the axial split of the pedicle
which is seen on the sagittal CT scan. There will be little comminution and
since the center of rotation is the anterior longitudinal ligament, the
posterior ligaments will be disrupted or the posterior neural arch is fractured
transversely. Flexion/distraction injury or seat belt injury can be purely bony,
purely ligamentous, or mixed. The treatment of flexion/distraction injury,
especially if the injury is ligamentous, is usually a posterior reconstruction
of the tension part of the spine with short segment fusion with
instrumentation. Ligamentous injuries of the spine do not heal (needs to be
fused). The bony chance fracture can be stable in extension and the fracture
can heal. The fracture could heal, but the fracture will probably need long
term follow-up. The fracture could be treated in a TLSO (Thoracic Lumbar Sacral
Orthosis) brace and watch the fracture for the development of kyphosis.
