Trigger Thumb

Description

Pediatric trigger thumb is caused by a mismatch between the flexor pollicis longus tendon and its sheath. Patients present with a hard, palpable nodule (Notta's node) at the base of the metacarpal and an inability to extend the thumb beyond 30 degrees, which can rarely be accompanied by triggering, snapping, or a digit locked in extension (summary by Wang et al., 2012).

Clinical Features

Weber (1979) observed a 2-year-old boy with stenosing tenovaginitis of the left thumb resulting in a flexion deformity of the interphalangeal joint of 30 degrees. The boy's father recalled that as a child he was unable to extend both thumbs. His condition had improved but at age 28 he still had weakness of both thumbs and definite 'triggering' bilaterally, with tendon nodules. Weber (1979) noted that a few familial cases had been reported but that this may have been the first report of affected parent and child.

Van Genechten (1982) described a 1-year-old boy who could not extend the interphalangeal joint of his right thumb. A firm, nontender nodule was palpable at the level of the metacarpophalangeal joint in the region of the flexor pollicis longus. Surgery revealed a nodule in the volar aspect of the flexor pollicis longus proximal to the main flexor sheath pulley and a mild degree of thickening of this annulus and adjacent sheath. The mother of the child mentioned that she and 4 other relatives had this anomaly and that all had been operated on in infancy with good results. No other congenital anomalies were present.

Wang et al. (2012) described monozygotic twin boys with mirror-image trigger thumbs.

Inheritance

The families with trigger thumb reported by Weber (1979) and Van Genechten (1982) suggested autosomal dominant inheritance.