The "Trigger" Thumb Locked in Extension - An Unusual Presentation of a Common Paediatric Condition.

Background: We report a variant of paediatric trigger thumb which is locked in extension rather than flexion. Methods: Eleven children with 14 trigger thumbs (three bilateral) locked in extension were reviewed retrospectively over a 12-year period. The number of flexed trigger thumbs encountered over this period was established from the operating room database. Results: All children were treated with release of the A1 pulley. Nine children achieved a full range of motion at the interphalangeal joint. One child with bilateral extended trigger thumbs required bilateral dorsal capsulotomy and another child developed temporary mild triggering in flexion. Conclusions: Approximately 1% of trigger thumbs treated operatively at this institution presented as the extended variant. Trigger thumb locked in extension should be considered in a child presenting with inability to flex the thumb.