Question:medium
Fallen fragment sign is seen in -
Fallen fragment sign is seen in -
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Which hollow, fluid-filled lesion lets a broken fragment drop freely inside it?
Updated On: Jun 23, 2026
- Simple bone cyst
- Osteosarcoma
- Adamantinoma
- Aneurysmal bone cyst
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: Reason from physics. For a bone fragment to literally fall and settle at the bottom of a lesion, the inside of that lesion must be a single open, fluid-filled space with nothing solid to stop it.
Step 2: Now classify the options. A simple (unicameral) bone cyst is exactly that - one cavity full of serous fluid. After a pathological fracture, a piece of cortex shears off and gravity carries it to the dependent wall, giving the fallen fragment sign.
Step 3: Eliminate the rest. Osteosarcoma and adamantinoma are solid, matrix-producing tumours, so a fragment has nowhere to fall. An aneurysmal bone cyst is divided by septa into multiple blood-filled chambers, which trap any fragment and prevent free settling.
Step 4: The sign is essentially diagnostic for a simple bone cyst with a healing pathological fracture, which is why option a is selected.
\[\boxed{\text{Simple bone cyst}}\]
Step 2: Now classify the options. A simple (unicameral) bone cyst is exactly that - one cavity full of serous fluid. After a pathological fracture, a piece of cortex shears off and gravity carries it to the dependent wall, giving the fallen fragment sign.
Step 3: Eliminate the rest. Osteosarcoma and adamantinoma are solid, matrix-producing tumours, so a fragment has nowhere to fall. An aneurysmal bone cyst is divided by septa into multiple blood-filled chambers, which trap any fragment and prevent free settling.
Step 4: The sign is essentially diagnostic for a simple bone cyst with a healing pathological fracture, which is why option a is selected.
\[\boxed{\text{Simple bone cyst}}\]
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