The ring butterfly fragment in diaphyseal fractures: its importance in flexible intramedullary nailing.

Ring butterfly fragment was described after it was noted to pose problems during insertion of flexible intramedullary nails. This fragment contains the entire circumference of the medullary canal or a substantial part of it. Once recognized preoperatively the fragment is reduced, providing a stable fracture configuration for fixation with flexible intramedullary nails. If the fragment is left displaced, it may lead to nonunion of the fracture; particularly after flexible intramedullary nailing of the tibia.