Spine: pseudosubluxation of C2: practice question

A Orthopaedics 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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Orthopaedics · Spine: pseudosubluxation of C2

Sample item

A 6-year-old who fell from a bed has no neck tenderness. A lateral cervical radiograph shows 3 mm anterior displacement of C2 on C3, which is thought to be physiological. Which line helps confirm this?

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

The answer and the reasoning

B. The posterior cervical line of Swischuk

Physiological anterior displacement of C2 on C3 is common in children under 8 years because of ligamentous laxity and horizontal facets. The posterior cervical line joins the posterior arch of C1 to the spinolaminar junction of C3, and in pseudosubluxation the spinolaminar line of C2 lies within 2 mm of it.

Option by option

  • A. McGregor line

    McGregor line is also a craniocervical line used for basilar invagination.

  • B. The posterior cervical line of Swischuk (correct)

    Correct. The Swischuk line separates pseudosubluxation from true injury at C2-C3.

  • C. Chamberlain line

    Chamberlain line assesses basilar invagination at the skull base.

  • D. The Power ratio

    The Power ratio assesses atlanto-occipital dissociation using the basion and posterior arch.

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.

More Orthopaedics questions

Questions about this Orthopaedics question

What is the answer to this Orthopaedics question?

The best answer is B, The posterior cervical line of Swischuk. Physiological anterior displacement of C2 on C3 is common in children under 8 years because of ligamentous laxity and horizontal facets.

Why is "McGregor line" not the answer?

McGregor line is also a craniocervical line used for basilar invagination.

Why is "Chamberlain line" not the answer?

Chamberlain line assesses basilar invagination at the skull base.

Why is "The Power ratio" not the answer?

The Power ratio assesses atlanto-occipital dissociation using the basion and posterior arch.

What concept does this question test?

It tests Spine: pseudosubluxation of C2 in Orthopaedics. The posterior cervical line joins the posterior arch of C1 to the spinolaminar junction of C3, and in pseudosubluxation the spinolaminar line of C2 lies within 2 mm of it.

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 Spine: pseudosubluxation of C2?

Pair each fracture with its classic complication and nerve injured. Then use the flashcards and the other Orthopaedics 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.