What causes hamburger bun sign in cervical spine on axial CT?
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Answer:
The hamburger bun sign is seen in normal cervical facet joints on axial CT imaging. It represents the typical appearance of healthy facet joints, where the superior articular surface of the lower vertebra forms the top bun, the joint space is the patty, and the inferior articular surface of the upper vertebra forms the bottom bun. This sign is not associated with pathology but serves as a baseline for identifying facet joint abnormalities such as dislocation.
Why is it called so?:
The sign is named for its resemblance to a hamburger, with the articular surfaces of the facet joint appearing as the top and bottom buns and the joint space as the patty in between. The term was introduced by Daffner and Daffner in their 2002 description of CT diagnosis of facet dislocations.
Pathophysiology:
In the normal cervical spine, the facet joints are oriented so that the articular surfaces face each other, creating a symmetrical, paired structure on axial CT. This orientation allows for smooth articulation and stability. The hamburger bun sign reflects this normal anatomical relationship.
Alternative names: Hamburger sign
Other associated named signs: Reverse hamburger bun sign, naked facet sign, headphones sign (seen in facet joint dislocation)
References
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
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