Bone: chronic osteomyelitis: practice question

A Pathology 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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Pathology · Bone: chronic osteomyelitis

Sample item

A 9-year-old boy in rural India had fever and distal femoral pain that was inadequately treated. Weeks later, radiographs show a fragment of dead bone surrounded by new bone, and a sinus discharges pus. Which component allows the infection to persist despite antibiotics?

ABrodie abscess formed in the cortexBInvolucrum, the periosteal new bone sleeveCSequestrum, the avascular necrotic bone that shelters bacteriaDCodman triangle from periosteal elevation

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

The answer and the reasoning

C. Sequestrum, the avascular necrotic bone that shelters bacteria

In haematogenous osteomyelitis, pus under pressure strips the periosteum and compromises the blood supply, causing necrotic bone (sequestrum). Periosteum lays down new bone around it (involucrum), and pus drains through cloacae and sinuses. Antibiotics do not penetrate avascular sequestra, so surgical removal is needed for cure.

Option by option

A. Brodie abscess formed in the cortex
Brodie abscess is a localised subacute abscess, not the necrotic fragment sheltering bacteria.
B. Involucrum, the periosteal new bone sleeve
Involucrum is vascular new bone and is not the persistent source of infection.
C. Sequestrum, the avascular necrotic bone that shelters bacteria (correct)
Correct. The sequestrum is an avascular reservoir that antibiotics cannot reach.
D. Codman triangle from periosteal elevation
Codman triangle is a radiographic sign of periosteal elevation, seen in osteosarcoma and sometimes infection.

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.

Questions about this Pathology question

What is the answer to this Pathology question?

The best answer is C, Sequestrum, the avascular necrotic bone that shelters bacteria. In haematogenous osteomyelitis, pus under pressure strips the periosteum and compromises the blood supply, causing necrotic bone (sequestrum).

Why is "Brodie abscess formed in the cortex" not the answer?

Brodie abscess is a localised subacute abscess, not the necrotic fragment sheltering bacteria.

Why is "Involucrum, the periosteal new bone sleeve" not the answer?

Involucrum is vascular new bone and is not the persistent source of infection.

Why is "Codman triangle from periosteal elevation" not the answer?

Codman triangle is a radiographic sign of periosteal elevation, seen in osteosarcoma and sometimes infection.

What concept does this question test?

It tests Bone: chronic osteomyelitis in Pathology. Periosteum lays down new bone around it (involucrum), and pus drains through cloacae and sinuses. Antibiotics do not penetrate avascular sequestra, so surgical removal is needed for cure.

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 Bone: chronic osteomyelitis?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.