Arthroplasty: metal-on-metal bearing: 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 · Arthroplasty: metal-on-metal bearing

Sample item

Five years after a metal-on-metal hip resurfacing, a woman has groin pain and a cystic mass near the hip. Serum cobalt and chromium are markedly raised and MRI shows a peri-articular fluid collection. What is the likely problem?

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

The answer and the reasoning

A. Adverse reaction to metal debris with a pseudotumour

Metal-on-metal bearings release cobalt and chromium particles, which can cause local tissue necrosis and a sterile inflammatory pseudotumour. Raised serum metal ions and MRI collections point to this diagnosis. Revision to a different bearing is often needed.

Option by option

  • A. Adverse reaction to metal debris with a pseudotumour (correct)

    Correct. Raised cobalt and chromium with a peri-articular collection indicate an adverse metal reaction.

  • B. Osteosarcoma of the femur

    Osteosarcoma would show a destructive bone lesion.

  • C. Simple trochanteric bursitis

    Trochanteric bursitis would not raise serum metal levels.

  • D. Gout of the hip

    Gout would show crystals in the joint and not raised metal ions.

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 A, Adverse reaction to metal debris with a pseudotumour. Metal-on-metal bearings release cobalt and chromium particles, which can cause local tissue necrosis and a sterile inflammatory pseudotumour.

Why is "Osteosarcoma of the femur" not the answer?

Osteosarcoma would show a destructive bone lesion.

Why is "Simple trochanteric bursitis" not the answer?

Trochanteric bursitis would not raise serum metal levels.

Why is "Gout of the hip" not the answer?

Gout would show crystals in the joint and not raised metal ions.

What concept does this question test?

It tests Arthroplasty: metal-on-metal bearing in Orthopaedics. Raised serum metal ions and MRI collections point to this diagnosis. Revision to a different bearing is often needed.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Arthroplasty: metal-on-metal bearing?

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.