A 30-year-old man dives into a shallow pool and lands on his head. CT of the cervical spine shows fractures of both anterior and both posterior arches of C1 with lateral displacement of the lateral masses. This injury pattern corresponds to which classification type, and what is its main clinical significance?

• A Type II odontoid fracture, unstable due to poor blood supply at the base of the dens
• B Hangman's fracture, unstable due to bilateral pedicle fracture of C2
• C Jefferson fracture, a burst fracture that may be unstable if the transverse atlantal ligament is ruptured ✓
• D Clay-shoveler's fracture, stable avulsion of the C7 spinous process

Explanation

Axial loading forces drive the occipital condyles into the lateral masses of A1, producing four-point arch fractures known as a Jefferson burst fracture. Instability depends on integrity of the transverse atlantal ligament, assessed by the sum of lateral mass displacement exceeding about 7 mm on open-mouth views. Hangman's fracture involves the pars interarticularis of A2, a completely different level and mechanism.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.