Congenital trigger thumb

Congenital stenosing tenosynovitis of the thumb is a result of a discrepancy between the size of the flexor pollicis longus tendon and the A1 pulley of the thumb's flexor tendon sheath. It may not be appreciated at birth due to the tendency to flex all digits. Both sides are involved in approximately 30% of children. There is an inability to extend the thumb interphalangeal joint fully and a nodule may be felt at the level of the metacarpophalangeal joint - Notta's node. The interphalangeal joint may be fixed in flexion or may still be mobile. Passive manipulation of the thumb into extension may be associated with a sudden release as the site of tendon thickening instantaneously escapes from the edge of the pulley.

Similar clinical features are present with a lesser frequency in congenital trigger finger and the condition can develop in adulthood - see submenu. The main differential is congenital clasped or clutched thumb.

About a third of cases resolve within a year. If the interphalangeal joint is still mobile during this time, there may be some role for passive manipulation and splintage. However, if the condition has not resolved by the age of 2 years, surgical A1 pulley release is indicated. No other treatment is successful. Unlike adult triggering of the thumb, there is little role for steroid injections in the child unless there is a rare, causative inflammatory condition for the tendon constriction eg rheumatoid arthritis.

To release the A1 pulley in the infant, under general anaesthetic and with loupe magnification an incision is made at the base of the thumb. This may be transversely within the creases or a chevron in shape. Blunt dissection is used to expose the flexor sheath thickening of the A1 pulley. Great care is taken to avoid damage to the digital nerves and vessels. The pulley is divided on its radial side; this is to avoid damaging the oblique pulley of the thumb. The wound is closed with an absorbable suture and a light dressing applied.