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.
There are some similarities in this condition as it presents in children versus adults. But for the most part pediatric trigger thumb and/or trigger finger are not the same as adults and should not be treated the same. An understanding of the basic problem may help explain these differences.
In both children and adults, 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.
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. Most of these surgeries are done with an open incision.
Surgery isn't always successful. There can be serious complications such as infection or failure of the wound to heal. The triggering can even come back. There may be no apparent reason for the recurrence of this condition but sometimes it's because the surgeon has failed to release enough of the flexor tendon sheath. Sometimes there is a failure to recognize the need for more than one procedure (release pulley AND divide the tendon) and that's why the problem comes back.
Overall treatment recommendations are as follows:
- Try conservative (nonoperative) care at first to see if the problem resolves spontaneously.
- Six months of splinting (keeping the thumb or finger straight at night while sleeping) is one approach.
- Don't wait more than two years for a natural healing to occur before doing surgery.
- 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).
- Open surgery reduces the risk of damage to the tiny blood vessels and nerves in children.
Hand therapy is not routinely needed after surgery. The patient is encouraged to move the finger as soon as the surgeon removes the soft dressing. There is a need for future studies to identify who should have surgery, what kind of surgery, and the optimal timing for surgery. And the natural history of both trigger finger and trigger thumb should be followed and reported on to help with treatment decisions.
Reference: Apurva S. Shah, MD, MBA, and Donald S. Bae, MD. Management of Pediatric Trigger Thumb and Trigger Finger. In Journal of the American Academy of Orthopaedic Surgeons. April 2012. Vol. 20. No. 4. Pp. 206-213.