Musculoskeletal imaging: atlantoaxial subluxation: practice question

A Radiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Radiology · Musculoskeletal imaging: atlantoaxial subluxation

Sample item

A woman with long-standing rheumatoid arthritis has neck pain and occipital headache. What would a flexion lateral cervical radiograph show to confirm atlantoaxial subluxation?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Atlantodental interval above 3 mm

Erosion of the dens and laxity of the transverse ligament in rheumatoid arthritis allow C1 to slip forward on C2, widening the atlantodental interval beyond 3 mm in adults on flexion. It can compress the cord and needs careful anaesthetic precautions.

Option by option

  • A. Bilateral C2 pars fractures

    Bilateral C2 pars fractures form a Hangman injury after hyperextension trauma.

  • B. Anterior wedging of the C5 body

    Anterior wedging of a mid-cervical body is a compression injury or deformity, not the finding of C1-C2 instability.

  • C. Atlantodental interval above 3 mm (correct)

    Correct. A widened atlantodental interval beyond 3 mm in an adult on flexion indicates atlantoaxial instability.

  • D. Fracture through the base of the dens

    A dens base fracture follows trauma, whereas rheumatoid subluxation arises from ligament laxity and erosion.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Radiology question

What is the answer to this Radiology question?

The best answer is C, Atlantodental interval above 3 mm. Erosion of the dens and laxity of the transverse ligament in rheumatoid arthritis allow C1 to slip forward on C2, widening the atlantodental interval beyond 3 mm in adults on flexion.

Why is "Bilateral C2 pars fractures" not the answer?

Bilateral C2 pars fractures form a Hangman injury after hyperextension trauma.

Why is "Anterior wedging of the C5 body" not the answer?

Anterior wedging of a mid-cervical body is a compression injury or deformity, not the finding of C1-C2 instability.

Why is "Fracture through the base of the dens" not the answer?

A dens base fracture follows trauma, whereas rheumatoid subluxation arises from ligament laxity and erosion.

What concept does this question test?

It tests Musculoskeletal imaging: atlantoaxial subluxation in Radiology. It can compress the cord and needs careful anaesthetic precautions.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Musculoskeletal imaging: atlantoaxial subluxation?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.