Inflammation: 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 · Inflammation: chronic osteomyelitis

Sample item

A 9-year-old boy had fever and pain in the distal femur treated late. Six weeks later a radiograph shows a dense fragment of devitalised bone lying within a cavity, surrounded by a shell of new subperiosteal bone, and there is a draining sinus. What is the dead bone fragment called?

AInvolucrumBSequestrumCCodman triangleDBrodie abscess

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

The answer and the reasoning

B. Sequestrum

In suppurative osteomyelitis the infected bone loses its blood supply and necroses, forming a sequestrum that bacteria shelter in and that sustains chronic infection. New bone laid down by the lifted periosteum around it is the involucrum. Chronic osteomyelitis therefore usually needs surgical removal of the sequestrum as well as antibiotics.

Option by option

A. Involucrum
The involucrum is the living new bone shell around the dead fragment, not the fragment itself.
B. Sequestrum (correct)
The sequestrum is the necrotic bone that persists inside the cavity.
C. Codman triangle
A Codman triangle is an elevated periosteal edge seen in aggressive tumours such as osteosarcoma and sometimes infection.
D. Brodie abscess
A Brodie abscess is a localised subacute abscess cavity in the metaphysis, not a piece of dead bone.

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 B, Sequestrum. In suppurative osteomyelitis the infected bone loses its blood supply and necroses, forming a sequestrum that bacteria shelter in and that sustains chronic infection.

Why is "Involucrum" not the answer?

The involucrum is the living new bone shell around the dead fragment, not the fragment itself.

Why is "Codman triangle" not the answer?

A Codman triangle is an elevated periosteal edge seen in aggressive tumours such as osteosarcoma and sometimes infection.

Why is "Brodie abscess" not the answer?

A Brodie abscess is a localised subacute abscess cavity in the metaphysis, not a piece of dead bone.

What concept does this question test?

It tests Inflammation: chronic osteomyelitis in Pathology. New bone laid down by the lifted periosteum around it is the involucrum. Chronic osteomyelitis therefore usually needs surgical removal of the sequestrum as well as antibiotics.

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 Inflammation: 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.