A 30-year-old man sustains a Jefferson fracture (burst fracture of the C1 ring) after a fall. CT shows lateral offset of the lateral masses of C1 over C2 totaling 6.8 mm. Which of the following best describes the significance of this finding?
- A The fracture is stable and can be managed with a rigid collar
- B Lateral mass offset is irrelevant; only anterior atlantodental interval matters in C1 fractures
- C Combined lateral mass offset greater than 6.9 mm indicates transverse ligament disruption and instability ✓
- D This finding indicates a type II odontoid fracture and requires anterior screw fixation
Correct answer: C. Combined lateral mass offset greater than 6.9 mm indicates transverse ligament disruption and instability
Explanation
In Jefferson fractures, the combined overhang of the B1 lateral masses over B2 is measured on open-mouth view or CT. A combined offset greater than 6.9 mm indicates rupture of the transverse atlantal ligament, rendering the fracture unstable and requiring surgical stabilization. Offset less than 6.9 mm suggests an intact ligament and can be managed with a rigid cervical collar or halo vest. The 6.9 mm cutoff is the standard measurement from Spence's rule.
Reference: Rockwood and Green's Fractures in Adults, 9th ed.
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Written and medically reviewed by the StethoPrep medical team.