Cyst-like defects following fractures in children.

Cyst-like cortical defects appearing a few weeks after a greenstick fracture in the undamaged part of the radius were observed in 9 children. Five children showed multiple lesions. These radiolucent cyst-like defects 2.4 to 48 mm proximal to the fracture line seemed to be situated within the zone of periosteal reaction. The diameter of the cyst-like defects varied from 3 to 7 mm, usually they were rounded or slightly oval. Fracture healing was unaffected. In three of the patients the lesions had disappeared on to three years later. We are convinced that these benign lesions are resorption cysts within the excessive periosteal reaction and related to the subperiosteal hematoma accompanying the greenstick fractures.