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Case Twenty Nine - Flexion-Distraction Fracture at L1 Vertebral Body

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Clinical History: A 26 year old man, s/p automobile accident seven weeks ago, presents to the outpatient orthopedic clinic in a Jewett brace complaining of a sore back with numbness in the L-1, L2 distribution. He was a belted driver in a high-speed, head-on collision.

Findings: The plain radiographs demonstrate anterior vertebral height loss totaling at least 70% and mild kyphosis (less than 20 degrees) at L1. Posterior vertebral body height was maintained. Careful examination of the radiographs reveal a horizontally oriented fracture through the left pedicle and transverse process, lamina and right pars interarticularis. Widening of the interspinous distance is present. No translation is identified.

Diagnosis: Flexion-distraction fracture at L1 vertebral body.

Discussion: It is important to be able to differentiate stable compression fractures from potentially unstable burst and flexion-distraction fractures of the thoracolumbar spine by plain radiograph. Accurate diagnosis is essential as treatment, for these fractures may be very different. The three column model of the spine by Denis and modified by McAfee defines flexion-distraction injuries as compressive failure of the anterior column and tension failure of the middle and posterior columns as a result of flexion about an axis posterior to the anterior longitudinal ligament and anterior to the PLL.

Radiographic signs of instability include:

  1. Interspinous and interlaminar widening
  2. Greater than 50% compression of the vertebral body
  3. Kyphosis of more than 20 degrees
  4. Translation of more than 2 mm
  5. Dislocation
  6. Interpediculate widening

If plain radiographic findings are suggestive of an unstable fracture, follow-up imaging with CT and/or MRI can be used. The choice of imaging is dependent on the presumed type of injury. MR is best for imaging of soft tissue injury (posterior ligament disruption and disc injury) and CT is best for imaging of fractures.

References:
Petersilge C. Thoracolumbar Burst Fracture: Evaluating Stability.
Seminars In Ultrasound, CT, And MRI, 1996; (17)2:105-113.

Denis F. The Three Column Spine and its Significance in the Classification
of Acute Thoracolumbar Spinal Injuries. Spine 1983;8:817.831.

Mcgrory BJ. Diagnosis of Subtle Thoracolumbar Burst Fractures. A New
Radiographic Sign. Spine 1993;18:2282-2285.

Gersbein SD. Rationale for the Management of Flexion-Distraction Injuries
of the Thoracolumbar Spine Based on a New Classification. Journal Of
Spinal Disorders 1989; (2)3:176-183.

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Submitted by:
Cheryl Petersilge, M.D.
Seth Goldsmith, MS-4.