The diagnosis of trigger thumb in children is usually made when the parents notice that the child cannot straighten the thumb all the way. The involved thumb is “bent” at the joint closest to the thumb nail.
Trigger thumb involves a thickening of the flexor tendon of the child’s thumb in the region of the metacarpophalangeal joint (the MP joint – on the palm side). These children usually have a bump or knot in this location that parents can easily feel.
Trigger thumb is rare – one estimate is that for every 1000 babies born, three of them may be affected by trigger thumb at one year of age. About 30% of children with trigger thumb have it on both sides.
Several explanations exist for pediatric trigger thumb:
- degeneration (wearing out) of the tendon in the thumb
- thickening of the tendon lining (synovium)
- positioning of the baby in the uterus may contribute to the thumb’s position or function
These are just theories, and there is no good scientific evidence to back them up. The ultimate cause is unknown.
This is often referred to as “congenital” (present at birth) trigger thumb, but multiple research studies of newborns have showed that it is not present at birth.
Most children are at least six months old when they develop the condition. Parents notice the flexed (bent) position of the thumb, often because the child injures some other area of the hand or wrist.
There may be painful locking, snapping, or clicking of the thumb, but the thumb is usually locked in a bent position. Sometimes parents don’t remember an injury; the child may deny hurting it, and may not complain of pain or discomfort at all.
Trigger thumb is usually diagnosed without x-rays. This is not a problem with the bones or joints in the thumb – the tendon (where the problem is) is not visible on regular x-rays. The surgeon may order x-rays if the diagnosis is not clear from examining the child.
No one knows exactly what percentage of trigger thumbs in kids will get better (resolve) over time. Several research studies have shown conflicting information on this; rates of improvement range from 0% (none get better) to 49%.
Most hand surgeons believe that chances of the thumb suddenly getting better may decrease as the child gets older.
Surgery for trigger thumb in children is very reliable. It involves cutting a tight, constrictive portion of the tendon sheath through a small incision. The incision is placed in one of the creases of the thumb, so the scar is minimized. Dissolvable sutures are used, so they don’t have to be taken out in the office.
Delaying surgery does not typically cause problems. Several research studies have shown good results from surgery even after delaying surgery for four years after parents noticed the symptoms.
Non-surgical methods such as simply waiting for spontaneous improvement, stretching, or splinting, may also be tried before deciding on surgery. There is currently no good science that tells us what results to expect with these methods.