Fractures and dislocations: stress shielding: 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 · Fractures and dislocations: stress shielding

Sample item

Years after insertion of a stiff cementless femoral stem, radiographs show resorption of the proximal medial femur with thickening of the cortex around the distal stem. What is the mechanism?

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

The answer and the reasoning

B. Load is carried by the stiff stem instead of the proximal bone, so the stimulus for bone maintenance is lost

Stress shielding follows Wolff's law: bone that is unloaded because a stiff implant takes the stress is resorbed. It is reduced by using more flexible stems, such as titanium, and by proximal loading designs. Polyethylene particle disease produces focal lytic areas near the joint line rather than a graded, load-related loss.

Option by option

  • A. Chronic low-grade infection of the stem

    Infection causes pain, raised inflammatory markers and a loosening pattern around the stem.

  • B. Load is carried by the stiff stem instead of the proximal bone, so the stimulus for bone maintenance is lost (correct)

    Correct. Unloading of bone by a stiff stem removes the stimulus to remodel, so it resorbs.

  • C. Macrophage response to polyethylene wear particles

    Particle-induced osteolysis produces localised lytic lesions around the cup and stem, not a pattern of proximal loss with distal hypertrophy.

  • D. Heterotopic bone formation in the muscle

    Heterotopic ossification forms bone in soft tissue and does not remove it.

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, Load is carried by the stiff stem instead of the proximal bone, so the stimulus for bone maintenance is lost. Stress shielding follows Wolff's law: bone that is unloaded because a stiff implant takes the stress is resorbed.

Why is "Chronic low-grade infection of the stem" not the answer?

Infection causes pain, raised inflammatory markers and a loosening pattern around the stem.

Why is "Macrophage response to polyethylene wear particles" not the answer?

Particle-induced osteolysis produces localised lytic lesions around the cup and stem, not a pattern of proximal loss with distal hypertrophy.

Why is "Heterotopic bone formation in the muscle" not the answer?

Heterotopic ossification forms bone in soft tissue and does not remove it.

What concept does this question test?

It tests Fractures and dislocations: stress shielding in Orthopaedics. It is reduced by using more flexible stems, such as titanium, and by proximal loading designs. Polyethylene particle disease produces focal lytic areas near the joint line rather than a graded, load-related loss.

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 Fractures and dislocations: stress shielding?

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.