Paediatric trigger thumb is estimated to represent about 2% of all upper extremity abnormalities in children. The incidence has been reported to be between 0.5 and 3 per 1,000 children. The flexor tendons of the hand and wrist (the tendons that help us bend) move freely in sheaths. The flexor tendons are held in place by a system of pulleys. If there is swelling of the tendon or of the tissue surrounding the tendon, the movement through the A1 pulley may be painful and inhibited. When the tendon is inflamed (nodule) it becomes too thick to pass through the A1 pulley. This can cause the thumb to have a snapping or lock into flexion when the thumb is being mobilised.

trigger-thumb

(image courtesy of stlorthopaedicspecialists.com)

Trigger thumb can also be painful over the area of the A1 pulley. In moderate to severe cases the thumb can often stay locked in a bent position until the thumb is forcibly pulled out straight. Trigger thumb can cause the thumb to completely lock/flex down, or sometimes it is only the thumb tip that locks down. We often see children who stop using the hand for play if their thumb continues to get stuck in a bent position as it makes it hard for them to grasp toys.      

The aetiology of trigger thumb in children remains unknown, but three possible causes have been suggested. First, it may be congenital and the flexor tendon may be too large or the pulley too small for the tendon to glide freely. Secondly, it may result from trauma and thirdly, the condition may develop during the early months of childhood.

When the thumb triggers it makes it extremely difficult to use the thumb. Especially to pinch and pick up objects.

Just like trigger thumb in adults, children can be treated with conservative management. At Riverina Hand Therapy, we custom make thermoplastic thumb splints which immobilise the thumb. Immobilisation of the thumb will rest the inflamed and irritated structures and aims to resolve the condition. We fabricated these splints so they are easy to put on and strong to withstand children’s activities!! If splinting does not resolve the triggering, then a surgical release of the pulley can be performed. With the pulley released, the flexor tendon will no longer become caught and cause triggering of the thumb.

Research has suggested that trigger thumb can spontaneously resolve in children, however, the longer they have the condition the less likely this is to occur. The sooner trigger thumb is treated, the better! In cases when the thumb stays locked down into flexion for many months or years, the harder it is for the child to be able to regain full functional use of the thumb. This is due to the soft tissues shortening and muscle weakness. An exercise programme will help the thumb to regain movement and strength again.  

At Riverina Hand Therapy, we see approximately 5-10 cases of paediatric trigger thumb a year. The earlier the trigger thumb is identified and treated, generally, the faster the child’s trigger thumb will resolve!