Unicameral bone cyst: fallen fragment sign

Case contributed by Dr Domenico Nicoletti


Pain after trauma.

Patient Data

Age: 6 years
Gender: Female

Pathological fracture through a proximal lytic lesion with smooth margins and narrow transition zone, and with a fragment in the dependent part (fallen fragment sign).

Annotated image

Yellow circle highlights position of the fallen bone fragment in the bone cyst. 

Case Discussion

Unicameral bone cysts are benign fluid containing lesions. The etiology is unknown. The cortical bone is not interrupted and the transition zone is narrow. There are usually asymptomatic, and are often an incidental finding, discovered before age 20. Sometimes they are diagnosed after pathological fracture. The typical location is the proximal end (metaphysis) of the humerus. Rare in other places, with the exception of the heel, in this location lipoma should be considered in the differential diagnosis.

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Case information

rID: 45857
Published: 10th Jun 2016
Last edited: 14th Aug 2019
Inclusion in quiz mode: Excluded

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