Trigger Thumb

What is trigger thumb?

Trigger thumb means your child’s thumb pops, clicks or catches when they try to straighten it. Their thumb may lock in a bent or straight position. If the thumb locks, your child can move it using their other hand. (Or you can move it for them.) But they can’t move the locked thumb using their thumb muscles.

In children, trigger thumb usually happens between the ages of 1 and 3 years old. It’s not thought to be due to injury or other medical problems.

Most children with trigger thumb have it in only 1 hand. About 1 child in 3 has it in both hands.

How does trigger thumb happen?

The muscle that bends the tip of the thumb is called flexor pollicis longus (FLEX-er PAHL-i-sis LONG-us). This muscle starts in your child’s forearm. Near the wrist, the muscle turns into tendon. The tendon runs along the palm side of your child’s thumb and connects to the bone in the tip of the thumb.

When your child moves their thumb, this tendon should glide smoothly inside a wrapping called a tendon sheath. Near the base of the thumb, a tough band (ligament) crosses the tendon and tendon sheath, acting like a pulley. Doctors call this the A1 pulley.

Trigger thumb happens when the tendon swells, forming a bump (nodule) near the A1 pulley. The nodule gets stuck at the pulley, so the tendon cannot glide inside the sheath. You may be able to feel this bump on your child’s palm at the base of their thumb.

Triggering can happen in fingers too. This is a different and more complex problem.

What are the symptoms of trigger thumb?

If your child has trigger thumb, they will have 1 or both of these symptoms:

• Popping, clicking or catching when they move their thumb
• Thumb locked in a bent or straight position

Your child may also have these symptoms:

• Pain and swelling in their thumb, usually near the base
• Bump on the palm side of their thumb, near the base

How is trigger thumb diagnosed?

Doctors can diagnose trigger thumb by asking about your child’s symptoms and doing a physical exam.

If your child seems to have trigger thumb, the doctor will check to make sure they do not have some other problem, like a broken bone or a joint that’s out of place (dislocated).

The doctor will also check for signs of broader health conditions that may affect the hands, like cerebral palsy or arthrogryposis. Most children with trigger thumb do not have any other condition.

How is trigger thumb treated?

Trigger thumb may get better on its own. Some children with trigger thumb need surgery so their thumb can move freely.

Observation

Trigger thumb in children often gets better over time without any special care. So, treatment usually begins with observation, or watching to see if the condition improves. The doctor will also consider if your child’s trigger thumb causes pain or if it gets in the way of your child using their hand for typical activities.

Surgery

If trigger thumb doesn’t get better by age 4 or if it is painful or harms your child’s function, your child may need a day surgery called trigger thumb release or A1 pulley release.

The surgeon makes a small cut (incision) on your child’s palm in the crease of skin at the base of the thumb. Then the surgeon cuts through the A1 pulley. This takes pressure off the tendon and allows it to glide smoothly. (The surgeon doesn’t cut into the tendon or remove the nodule.)

After surgery, your child will need a cast for 2 weeks to protect and stretch their thumb while it heals. Trigger thumb rarely comes back, and children rarely need any other treatment for it. You can expect your child to regain typical use of their thumb.