Arthroplasty: Charnley low friction principle: 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: Charnley low friction principle

Sample item

Sir John Charnley's low friction arthroplasty improved the longevity of hip replacement. Which design feature was central to it?

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

The answer and the reasoning

B. A small femoral head, with a high-density polyethylene cup, both fixed with bone cement

Charnley used a small (22 mm) stainless steel femoral head against a high-density polyethylene socket, fixed with polymethylmethacrylate cement. A small head reduces frictional torque and so the load transferred to the cement interface. This design became the standard for decades.

Option by option

  • A. A ceramic head on a ceramic liner

    Ceramic-on-ceramic bearings are a later development.

  • B. A small femoral head, with a high-density polyethylene cup, both fixed with bone cement (correct)

    Correct. A small head on polyethylene, with cement, defines the Charnley prosthesis.

  • C. A large metal head articulating on a metal cup

    Metal-on-metal bearings were used in other designs.

  • D. An uncemented porous coated stem

    Uncemented porous stems came later and are not Charnley's design.

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 B, A small femoral head, with a high-density polyethylene cup, both fixed with bone cement. Charnley used a small (22 mm) stainless steel femoral head against a high-density polyethylene socket, fixed with polymethylmethacrylate cement.

Why is "A ceramic head on a ceramic liner" not the answer?

Ceramic-on-ceramic bearings are a later development.

Why is "A large metal head articulating on a metal cup" not the answer?

Metal-on-metal bearings were used in other designs.

Why is "An uncemented porous coated stem" not the answer?

Uncemented porous stems came later and are not Charnley's design.

What concept does this question test?

It tests Arthroplasty: Charnley low friction principle in Orthopaedics. A small head reduces frictional torque and so the load transferred to the cement interface. This design became the standard for decades.

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 Arthroplasty: Charnley low friction principle?

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.