The tendons that bend the thumb pass through a series of ligamentous pulleys, which hold the tendons close to the bones. Normally, the tendons and the pulleys have a slick lining (tensoynovium), allowing for easy gliding of the tendons as they pass through the pulley.
In pediatric trigger thumb, the soft tissues that make up the first pulley at the base of the thumb become thickened. The pulley may become constricted around the tendon and the tendon may develop a nodule. This prevents the tendon from moving freely through the pulley. The constant irritation of the tendon moving back and forth causes increased swelling and more irritation. This can lead to clicking, catching, or locking of the thumb.
Pediatric trigger thumb is not the same condition seen in adults, but they are similar. In children, pediatric trigger thumb is an acquired condition – which means it is not present at birth (congenital). It simply develops around 18-24 months of age. Most often the thumb is stuck in the bent position. However, if the thumb does click it usually doesn’t hurt. In adults, trigger thumb (or trigger finger) is usually related to overuse, trauma, injury, or is associated with other medical conditions. In adults, the triggering is usually painful.
Causes of Pediatric Trigger Thumb
There is no clear reason why some children develop pediatric trigger thumb. In children with pediatric trigger thumb, 20% have it on both hands and 10% have a family history – a sibling or parent who also had pediatric trigger thumb.
A common cause is a mismatch in size between the flexor tendon and the pulley. As your child moves their thumb, it may sometimes click or lock. Usually, the thumb locks (gets stuck) in a bent position – this is called a flexion contracture. This means that the child cannot actively, or sometimes even passively, straighten the thumb. Rarely does the thumb lock in a
- Increased swelling or irritation when moving the thumb
- Moving the thumb can lead to clicking, catching or locking of the thumb
Some children may “grow out of” pediatric trigger thumb given enough time. Healing happens gradually and the condition resolves on it’s own. This is called a spontaneous recovery. This course of treatment is very unpredictable and may take up to five years.
Keeping the thumb straight at night or while sleeping may help decrease irritation and swelling around the tendon or pulley. Splints should be used consistently for 6 months. However, this treatment is only appropriate if the thumb can be straightened.
Unfortunately, most children do not grow out of pediatric trigger thumb and require surgery to “unlock” the tendon and allow full motion of the thumb.
If splinting can not or has not improved the condition, your provider may recommend surgery. It is a very simple, painless, and successful surgery. Your child’s hand surgeon will explain the, risks and benefits of surgery.