Incidence and development of trigger thumb in children.

PURPOSE: Whether trigger thumb is congenital or acquired remains controversial. The purpose of this study was to identify whether trigger thumb is present at birth and to clarify whether trigger thumb represents a developmental condition.

METHODS

We examined 1,116 babies born at Yamagata Prefectural Nihonkai Hospital within 14 days after birth. All patients were examined by the author (N.K.), a hand surgeon. Patients were followed up to determine whether trigger thumb would present later even though it was not present at birth. We informed parents about the development of trigger thumb by providing informational sheets for neonatal screenings after hospital discharge. They were asked to check their child for a year or more to see if any flexion deformity of the interphalangeal joint of the thumb occurred. After discharge from the hospital, the family was responsible for noticing trigger thumb in their infant and seeking medical treatment.

RESULTS

Trigger thumb was not identified in any patient at birth. Responses were obtained from 601 families. Trigger thumb manifested in 2 thumbs of 2 children in the screening group at 8 and 11 months after birth; however, 3 additional children developed trigger thumb at 15, 21, and 30 months of age.

CONCLUSIONS

The incidence of acquired trigger thumb in children 1 year of age was 3.3 per 1,000 live births. It is unlikely that this study identified all cases of trigger thumb in patients older than 1 year in the primary screening group. The results of this follow-up study, however, suggest that trigger thumb is not present at birth but develops with postnatal growth.