Ortho Hors D'oeuvres (Answer):
To review, this is a 64 year-old female presenting with back pain after low speed motor vehicle collision.
Questions and Answers:
1) What is the key finding on x-ray? What is its eponym?
There is a fracture of the L2 vertebra. The anterior column of the L2 vertebra has been compressed by approximately 30% (red arrow). The blue arrow demonstrates a transverse fracture through the spinous process of the same vertebra. This fracture is called a "Chance fracture," and it is typically caused by hyperflexion mechanisms, such as ones sustained by patients wearing lapbelts only in the setting of motorvehicle collisions.
When counting lumbar vertebrae, remember that L5 sits on top of the sacrum, and is usually bisected by the illiac crest in the lateral view.
2) What are the injuries associated with this finding?
Chance fractures are highly correlated with intra-abdominal injuries. 33% of patients with Chance fractures had intra-abdominal injuries, the majority of which were hollow viscus injuries. On reassessment of this patient, she had the following right upper quadrant fast:
She was immediately transferred to the trauma center, where she was diagnosed with a grade III liver laceration and sent to the ICU for transfusion and observation.
3) Is this a stable or unstable injury?
The lumbar and thoracic spinal column is supported by three "columns" of stability: the anterior, the middle, and the posterior spinal column. Generally speaking, an injury must leave two out of three columns intact in order to be considered stable. Even then, if there is significant compression of the anterior column (for example, in a compression fracture > 10-30%) it may still be considered unstable.
In Chance fractures, the anterior column has been compressed and the posterior column has been extended under strain. In order to assess for stability, the patient must undergo an MRI to assess for intact posterior ligaments. Even if the posterior ligaments are intact, the patient will need a TLSO for several months while the bones heal.
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Chapman JR, Anderson PA. Thoracolumbar spine fractures with neurologic deficit. Orthop Clin North Am. 1994;25(4):595.
Tyroch AH et al. The association between Chance fractures and intra-abdominal injuries revisited: a multicenter review. Am Surg. 2005 May;71(5):434-8).