Trigger finger and trigger thumb are conditions affecting the movement of the tendons as they bend the fingers or thumb toward the palm of the hand. This movement is called flexion. Trigger thumb is much more common than trigger finger among babies and young children.
the tendons that move the fingers are held in place on the bones by a series of ligaments called pulleys. These ligaments form an arch on the surface of the bone that creates a sort of tunnel for the tendon to run in along the bone.
To keep the tendons moving smoothly under the ligaments, the tendons are wrapped in a slippery coating called tenosynovium. The tenosynovium reduces the friction and allows the flexor tendons to glide through the tunnel formed by the pulleys as the hand is used to grasp objects.
Triggering is usually the result of a thickening in the tendon that forms a nodule, or knob. The pulley ligament may thicken as well. The constant irritation from the tendon repeatedly sliding through the pulley causes the tendon to swell in this area and create the nodule.
In children, trigger thumb or finger is an acquired (not congenital or present at birth) condition. In other words, the child isn’t born this way but instead, develops the condition early on. A common anatomic cause of trigger thumb is a mismatch in the size of the flexor tendon and the pulley.
Trigger thumb or finger in children is not from overuse, trauma, or injury (those are more common causes in adults). And in children, the thumb is more likely to be fixed or stuck in what is referred to as a flexion contracture rather than a true triggering mechanism. Flexion contracture means the child cannot actively (or sometimes cannot even passively) straighten the thumb.
No one really knows the reason why some children develop these triggering digits. There are plenty of theories but no actual scientific evidence to explain it. Likewise, little is known about the natural history of trigger thumbs/fingers. And that is what you are asking about.
Natural history refers to what happens over time without treatment. As with many other orthopedic problems in children, there are a significant number of children who experience a gradual healing or resolution of the condition. This type of spontaneous recovery takes up to two years and is unpredictable. In other words, there’s no way to tell which children will “grow out of it.”
The majority of children do not grow out of it and require surgery to remove the nodule holding the tendon back, to release the stuck pulley mechanism, or to cut the tendon or lining around the tendon. This last treatment technique is used when the tendon isn’t gliding inside the tendon sheath like it should.
At this time, expert opinion is that conservative (nonoperative) care should be tried first to see if the problem resolves spontaneously. Six months of splinting (keeping the thumb or finger straight at night while sleeping) is another possible approach.
Families should not wait more than two years for a natural healing to occur before considering surgery. And there is some limited research suggesting that surgical release is better done sooner than later (e.g., by age three rather than waiting five or six years). Your orthopedic surgeon is really the best one to evaluate the child and advise you.