Paediatric Trigger-Locked Thumb.

Paediatric trigger-locked thumb (PT-LT) is a common paediatric thumb condition. It is an acquired flexion deformity of the interphalangeal joint because of a size mismatch between an enlarged flexor pollicis longus tendon and a stenotic oblique pulley. It may present clinically as paediatric locked thumb which is more common or infrequently as paediatric trigger thumb. Paediatric locked thumb is classified into two types based on the presence of metacarpophalangeal joint (MCPJ) hyperextension. Type I does not have MCPJ hyperextension, whereas type II is associated with MCPJ hyperextension. The treatment of PT-LT is determined by the patient's age, time of onset, presentation, and type. Treatment modalities are observation, splinting, therapy, or surgery. Surgery involves dividing the A1 pulley and, most importantly, part of the oblique pulley. Level of Evidence: V (Therapeutic).