We tried to define the etiology of the trigger thumb in children, to know the main symptom of the trigger thumb in children and to conclude the prophet age to operate without residual symptoms nor complications.

1) 50 Children, 60 thumbs operated in our hospital (A1 pulley release after the age of 2) were included in this study. 2) In 7407 newborn babies born in our hospital, screening test were performed for detection of trigger thumb in nursery and also follow-up (180 days or more) for detection of trigger thumb was performed.

1) In 50 children underwent operation, only two (4%) had the deformity at the day of birth. All the babies (100%) had flexion contractures of the interphalangeal joint of the thumb. The nodule was found in 48 (80%) of 60 thumbs. The triggering, however, was found in only 16 thumbs (27%) . The patients underwent operation after the age of 4 (11 patients, 22%) had no complication nor residual symptom. 2) In the screening of 7407 newborn babies, nobody had flexion contractures of the thumb at the day of birth.

1) The main symptom of the trigger thumb in children was "flexion contracture", not "triggering". 2) The children operated after the age of 3 or 4 is expected to get good result.3) The trigger thumb in children is seemed to be "acquired" or "developmental" rather than "congenital".