Unicameral bone cyst


Two radiographs of a pathologic fracture in a simple bone cyst of the proximal humerus. Within the cyst is noted a small, thin, linear bony fragment that is displaced from the site of the fracture. An excellent sign of unicameral bone cyst. The fallen fragment secondary to pathologic fracture is pathognomonic for this cyst. A portion of the wall of the cyst has undergone a pathological fracture and has subsequently floated down (fallen) via gravity into the dependent portion of the cyst.


McGlynn FJ, Mickelson MR, El-Khoury GY: The fallen fragment sign in unicameral bone cyst. Clin Orthop 1981 May;(156):157-9.

Killeen KL.: The fallen fragment sign Radiology 1998 Apr;207(1):261-2 .

Struhl S, Edelson C, Pritzker H, Seimon LP, Dorfman HD: Solitary (unicameral) bone cyst. The fallen fragment sign revisited. Skeletal Radiol 1989;18(4):261-5.


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