Transient posttraumatic cystlike lesions of bone.

Cystlike cortical defects appearing after minor greenstick fractures in children have occasionally been described. These lesions are typically asymptomatic and appear just proximal to the fracture line within the area of subperiosteal new bone formation. Although the pathogenesis of these lesions remains in doubt, complete resolution is the rule, with no adverse effect on fracture healing. Only 18 cases of these transient postfracture cysts have previously been reported in the English-language literature. We present two additional cases of cyst formation after greenstick fracture of the distal radius in children aged 2.5 and 5.5 years. The natural history of such lesions is discussed and the current theories on their pathogenesis are reviewed.