Trigger finger, or trigger thumb, is a type of stenosing tenosynovitis (specifically digital tenovaginitis stenosans) in which the sheath around a tendon in a thumb or finger becomes swollen, or a nodule forms on the tendon. In such a condition, repetitive forceful use of a digit leads to narrowing of the fibrous digital sheath in which it runs. This leads to stenosis of the osseofibrous tunnel of the finger. If tendons of the flexor digitorum superficialis or flexor digitorum profundus muscles become enlarged proximal to the tunnel, the affected individual is unable to extend his/her finger. Affected digits may become painful to straighten once bent, and may make a soft crackling sound when moved. More than one finger may be affected at a time, though it usually affects the thumb, middle, or ring finger. The triggering is usually more pronounced in the morning, or while gripping an object firmly.
It is called trigger finger because when the finger unlocks, it pops back suddenly, as if releasing a trigger on a gun.
Trigger finger is usually idiopathic.
There is some evidence that idiopathic trigger finger behaves differently in patients with diabetes.
As with many other hand and arm conditions, some speculate that work activities may be associated with trigger finger; however, this is largely speculative with little scientific support.
Injection of the tendon sheath with a corticosteroid is effective over weeks to months in more than half of patients.
The problem is predictably resolved by a relatively simple surgical procedure (usually outpatient, under local anesthesia). The surgeon will cut the sheath that is restricting the tendon.
Investigative treatment options with limited scientific support include: non-steroidal anti-inflammatory drugs, occupational or physical therapy, steroid iontophoresis treatment, splinting, therapeutic ultrasound, phonophoresis (ultrasound with an anti-inflammatory dexamethasone cream), and Acupuncture.
Difficulty extending the proximal interphalangeal joint may persist for months and benefits from exercises to stretch the finger straighter.
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