What Is This Thumb Anomaly?

THE CASE: This thumb anomaly in a 16-month-old boy was noted within the first month of life. The mother heard an occasional popping sound when trying to straighten the thumb. The infant also had subcoronal hypospadias. He was otherwise healthy.

Answer and discussion on next page.

Trigger thumb is the correct answer.

DISCUSSION: Pediatric trigger thumb is a stenosing tenosynovitis of the flexor pollicis longus tendon with flexion deformity of the interphalangeal joint. The common presentation is a fixed flexion deformity of the thumb on one hand or bilaterally. Trigger thumb is rarely seen in infants, although it accounts for 85% of all cases of trigger digits in childhood.^1,2

The differential diagnosis includes congenital clasped thumb (thumb is held tightly beneath the flexed fingers) and congenital absence of the extensor pollicis longus (limp thumb). Trigger thumb may also be part of a syndrome, such as trisomy 13 syndrome.³

It remains unclear whether this is a congenital condition. In most cases, a specific cause is not determined, although there is evidence for a genetic predisposition. A family history of trigger finger may be obtained in some cases. An autosomal dominant pattern of inheritance has been suggested.³ Trauma is an unlikely cause.

The presence of 2 or more congenital conditions, such as in this patient, may point toward a genetic syndrome. However, a literature search revealed no significant correlation between trigger thumb and hypospadias. These 2 conditions were thought to be isolated anomalies; no genetic workup was done.

Infants with trigger thumb can be observed or treated conservatively with daily home stretching exercises. Often the digit can be straightened with passive stretching or splinting or both. However, in some cases the deformity may be rigid. One study showed that in the first 4 years of life, spontaneous resolution occurred in more than 60% of patients; in those who did not have resolution, more than 80% had some improvement in flexibility.⁴ Surgical correction may be considered for a trigger thumb that persists after this time.

Case and image courtesy of Peter Noronha, MD, and Imteyaz Khan, MD of the University of Illinois at Chicago. 

References:

REFERENCES:

1. Moon WN, Suh SW, Kim IC. Trigger digits in children.

J Hand Surg Br

. 2001;26:11-12.
2. Cardon LJ, Ezaki M, Carter PR. Trigger finger in children.

J Hand Surg Am

. 1999;24:1156-1161.
3. Ogino T. Trigger thumb in children: current recommendations for treatment.

J Hand Surg Am

. 2008;33:982-984.
4. Baek GH, Kim JH, Chung MS, et al. The natural history of pediatric trigger thumb.

J Bone Joint Surg Am

. 2008;90:980-985.