title: The fallen fragment sign in unicameral bone cyst.
abstract: The roentgenographic findings in unicameral bone cyst may be difficult to differentiate from a solid tumor of bone. When present, the fallen fragment sign may aid in determining the roentgenographic diagnosis of unicameral bone cyst. In this finding, with a pathologic fracture a fragment of cortical bone may become dislodged and gravitate to the dependent portion of the unicameral bone cyst. Two examples of the fallen fragment sign demonstrate the displacement of a fragment of cortical bone to the dependent portion of the cystic cavity.
mesh_terms: D001845:Bone Cysts / Q000150:complications / Q000000981:diagnostic imaging*; D001859:Bone Neoplasms / Q000000981:diagnostic imaging; D002648:Child; D003937:Diagnosis, Differential; D050723:Fractures, Bone / Q000150:complications / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D011859:Radiography