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What is congenital trigger thumb?
Paediatric trigger thumb is a condition seen in children where the thumb is locked in a flexed position and cannot be straightened (Figure 1). It is a fairly common condition affecting about 3 per 1,000 children below the age of 1 year. In about 25% children the deformity affects both hands.

Congenital Trigger Thumb

 

What causes congenital trigger thumb?
The flexor pollicis longus (FPL) tendon on the volar aspect of the thumb is covered by it’s tendon sheath (Figure 2).

Congenital Trigger Thumb

In Paediatric trigger thumb, the tendon of flexor pollicis longus (FPL) is thickened due to abnormal collagen degeneration and synovial proliferation. The thickened tendon can be felt at the base of the thumb and is called “Notta’s node”. The exact cause for this is not known. Due to this, the tendon gets entrapped within the surrounding sheath (Figure 3).

Congenital Trigger Thumb

Congenital trigger thumb usually begins with thumb triggering, that is, on flexing the thumb, the Inter-Phalangeal joint gets stuck in a position of flexion, however with passive extension the thumb opens out with a “snap”.

Over a period of time, the condition progresses to a “locked trigger thumb”. Once that happens, the thumb is locked in a flexed position and cannot be straightened to an extended position. Locking typically occurs around the age of one year. As mentioned earlier, the “Notta’s node” can be palpated at the thumb base (Figure 4).

Congenital Trigger Thumb

Xrays done in congenital trigger thumb are normal as there is no bony abnormality.

 

What is the treatment of congenital trigger thumb?

When a child with congenital trigger thumb is first seen, non-operative treatment may be initially attempted. Non-operative treatment consists of physiotherapy, stretching exercises and splints/taping to maintain the thumb in a straightened position. Non-operative treatment is successful in almost 50% children seen before the age of one year and when the thumb is not yet locked.

However, operative treatment is needed once the thumb is locked. Surgery in congenital trigger thumb consists of A1 pulley release wherein the sheath surrounding the FPL tendon is released and the entrapped tendon is freed.

Results of surgery are extremely good and recurrence / complications after this surgery are rare.

Congenital Trigger thumb

Congenital Trigger Thumb

Posted in public interest by Division of Children’s Orthopaedics, Pinnacle Orthocentre Hospital. For more information, mail drsvvaidya@gmail.com. To schedule an appointment, call 7028859555.