Here’s something pediatricians and parents of young children will want to know. Viral infections can cause trigger finger. It doesn’t happen very often but it should be a consideration when evaluating cases of unexplained trigger finger.
What is trigger finger? 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.
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.
What causes trigger finger? In children, triggering can be caused by a congenital defect that forms a nodule in the tendon. Type 1 diabetes has also been linked with trigger finger in children and teens. In adults, rheumatoid arthritis, partial tendon lacerations, repeated trauma from pistol-gripped power tools, or long hours grasping a steering wheel can cause triggering.
In the case of the seven-year-old who is the subject of this report, viral infection caused damage to the synovium and a rounded swelling (nodule) to form in the tendon. The authors wrote this case up to help highlight the fact that viral infections can indeed be a triggering mechanism for trigger finger. It’s a rare, but important, factor to keep in mind when evaluating a child with trigger finger.
What does trigger finger look like? The symptoms of trigger finger can include pain and a funny clicking sensation when the finger is bent and straightened. Tenderness usually occurs over the area of the nodule, at the bottom of the finger or thumb.
The clicking sensation occurs when the nodule moves through the tunnel formed by the pulley ligaments. With the finger straight, the nodule is at the far edge of the surrounding ligament. When the finger is flexed, the nodule passes under the ligament and causes the clicking sensation. If the nodule becomes too large it may pass under the ligament, but it gets stuck at the near edge. The nodule cannot move back through the tunnel, and the finger is locked in the flexed trigger position.
How does the physician know a viral infection is the cause of trigger finger? In this case, the child had been seen first for hip pain and limping. There was no fever and no history of trauma. Lab tests showed an elevated erythrocyte sedimentation rate (ESR or “sed” rate). The sed rate is a sign of inflammation. Ten days later, he came in to the clinic with trigger finger affecting the ring finger of both hands. Anytime a problem occurs on both sides (called bilateral), the physician has cause to suspect an underlying systemic problem.
What’s the treatment for viral-induced trigger finger? Like any viral infection, rest and plenty of fluids are advised. Antibiotics are not helpful as there is no bacterial component to the illness. And since the trigger finger symptoms went away after a month’s time, the authors felt their plan of care was right on target. This result to a wait-and-see approach is important because most cases of trigger finger (caused by something other than a virus) usually require surgery.
Thus the trigger finger condition caused by a viral infection is considered benign (not life-threatening), transient (symptoms come and go or move around as in this case), and self-limiting (temporary and will go away). Why only the hip on one side and both ring fingers were affected in this case remains unknown.