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Orthopaedics · Hip: MRI double line sign in AVN
Sample itemMRI of the hip in a young man on long-term steroids shows a serpiginous margin of the necrotic segment, with a bright inner line and a dark outer line on T2 images. What is this sign?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
D. Double line sign of avascular necrosis
The double line sign is a characteristic MRI finding in avascular necrosis. The outer dark line is reactive sclerosis, and the inner bright line is vascular granulation tissue. It is highly specific and can identify disease before radiographs change.
Option by option
A. Bone marrow oedema of transient osteoporosis
Transient osteoporosis shows diffuse marrow oedema without a serpiginous rim.
B. Crescent sign of cartilage loss
The crescent sign is a radiographic sign of subchondral collapse.
C. Shenton line disruption
Shenton line is a radiographic arc used for hip development and displacement.
D. Double line sign of avascular necrosis (correct)
Correct. A bright inner line within a dark outer rim is the double line sign of AVN.
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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