Trigger thumb is a condition in which the thumb joint locks and does not straighten out when trying to flex the thumb. The medical term for trigger thumb and trigger finger is stenosing tenosynovitis. Stenosing refers to the fact that the sheath that surrounds the thumb's tendons becomes more narrow than normal. Tenosynovitis is the inflammation of the tendon, which contributes to the limited range of motion. Trigger thumb in infants might look strange but poses no discomfort.
Trigger thumb, and the more common trigger finger, which denotes tenosynovitis in other fingers, is more common in adults, but the symptoms can occur in small children, according to Australia's Wesley Hand Centre. As noted in a 2000 issue of the "Journal of Bone and Joint Surgery," some children are born with a trigger thumb.
In adults, trigger thumb can be the result of a repetitive strain injury, but the thickening of the tendon in the thumb that creates the locked positioning can be present in even the youngest of babies for reasons that are not quite understood, explains the Wesley Hand Centre. Older research performed on the condition and reported in a 1949 issue of the "Journal of Bone and Joint Surgery" theorizes that the condition might be inherited, especially when a baby is born with a trigger thumb.
Babies who suffer from trigger thumb do not experience pain but cannot straighten out their thumb from a bent position. The swollen or thickened synovial tendon might form a small knot or mass under the skin of the thumb, which does not hurt. The knot moves around when the abnormal thumb is manipulated. Older people who develop trigger fingers might hear a clicking sound when bending and flexing the affected digit before the joint locks up, but this is not always the case with younger patients.
Infant trigger thumb often clears up on its own in a phenomenon called spontaneous recovery. Researchers from the Royal Hospital for Sick Children in Scotland found that almost half of the children studied recovered without medical intervention, though most of the children were older than 1 year. Treatment for older people who experience pain with their limited range of motion might include splinting and steroid injections to encourage a reduction in swelling. The Wesley Hand Centre recommends a "wait and see" approach for infants with trigger thumb, as many cases reverse without treatment. Surgical release of the constricted tendon might be required if the child's thumb does not spontaneously recover by his third birthday.
According to the 1949 and 2000 research documented in the "Journal of Bone and Joint Surgery," the outcome for infants and children with trigger thumb is positive. Recurrence rates post-surgery or spontaneous recovery are relatively low, at an estimated 4 percent. Range of motion and muscle strength in the hand usually are not affected.