Unicameral bone cyst with fracture and fallen fragment sign

Case contributed by A.Prof Frank Gaillard


Child presenting with severe pain in arm following a minor fall.

Patient Data

Age: Child
Gender: Male

X-ray humerus

Modality: X-ray

Two x-rays of the right humerus demonstrate a lucency within the proximal diaphysis with slight expansion and a fracture. Lying medially within the cyst is a fragment of cortex.

Fallen fragment sign

Modality: Annotated image

The so called "fallen fragment sign" is specific for a unicameral bone cyst, with pathological fracture. Part of the thinned cortex 'falls' into the cyst, thus indicating that the lucency is A) fluid B) uni-loculated.  

Distribution of unicameral bone cysts

Modality: Diagram


Case Discussion

Typical appearances of a large unicameral bone cyst with a pathological fracture and fallen fragment sign. 

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Case Information

rID: 12551
Case created: 15th Dec 2010
Last edited: 25th Dec 2015
Tag: humerus
Inclusion in quiz mode: Included

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