Hip: Caisson disease: 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 · Hip: Caisson disease

Sample item

A deep-sea diver who ascended rapidly in the past develops chronic hip and shoulder pain. Radiographs show a mottled sclerotic head of the femur and humerus. What is the likely cause?

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

The answer and the reasoning

D. Dysbaric osteonecrosis from nitrogen bubbles obstructing the circulation

Rapid decompression allows nitrogen bubbles to form in blood and fat, blocking the small vessels of bone. This causes avascular necrosis, most often in the femoral and humeral heads. It is called Caisson disease or dysbaric osteonecrosis.

Option by option

  • A. Paget disease of bone

    Paget disease causes a thickened coarse trabecular pattern in older adults.

  • B. Septic arthritis from marine organisms

    Septic arthritis presents acutely with fever and effusion rather than chronic mottled sclerosis.

  • C. Osteoarthritis from repeated trauma

    Osteoarthritis causes joint space narrowing and osteophytes and not mottled sclerosis of the heads.

  • D. Dysbaric osteonecrosis from nitrogen bubbles obstructing the circulation (correct)

    Correct. Nitrogen emboli cause avascular necrosis in divers.

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 Orthopaedics question

What is the answer to this Orthopaedics question?

The best answer is D, Dysbaric osteonecrosis from nitrogen bubbles obstructing the circulation. Rapid decompression allows nitrogen bubbles to form in blood and fat, blocking the small vessels of bone.

Why is "Paget disease of bone" not the answer?

Paget disease causes a thickened coarse trabecular pattern in older adults.

Why is "Septic arthritis from marine organisms" not the answer?

Septic arthritis presents acutely with fever and effusion rather than chronic mottled sclerosis.

Why is "Osteoarthritis from repeated trauma" not the answer?

Osteoarthritis causes joint space narrowing and osteophytes and not mottled sclerosis of the heads.

What concept does this question test?

It tests Hip: Caisson disease in Orthopaedics. This causes avascular necrosis, most often in the femoral and humeral heads. It is called Caisson disease or dysbaric osteonecrosis.

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 Hip: Caisson disease?

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.