Trigger finger, or trigger thumb, is a type of stenosing tenosynovitis in which the sheath around a tendon in a thumb or finger becomes swollen, or a nodule forms on the tendon. In either case, the tendon can no longer slide freely through its sheath. 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.

Treatment

The two mainstays of treatment are 1.corticosteroid injection directly around the tendon and sheath and 2. surgical release of the sheath.

One or two corticosteroid injections resolve the problem more than 50% of the time, and may be slightly less effective in diabetics. [1] It is unusual to give more than 2 or 3 corticosteroid injections, primarily because too many injections can weaken local tissues and can cause skin atrophy and discoloration. Injections work by reducing the size of the nodule on the tendon and this can take weeks to months.

Operative treatment provides more rapid and predictable relief, but is most often used when corticosteroid injections are unsuccessful. The problem is resolved by a relatively simple surgical procedure (usually outpatient, under local anesthesia). The surgeon will cut the sheath that is restricting the tendon.

Alternative treatments including occupational or physical therapy (including steroid iontophoresis treatment, splinting, therapeautic ultrasound to decrease swelling or phonophoresis (ultrasound with an anti-inflammatory dexamethasone cream) and Acupuncture have limited scientific support and a more limited role in treatment.

Recovery

The natural history of idiopathic trigger finger (what happens if you don't treat it) is not well studied and is incompletely defined.

Resolution of triggering can be delayed for weeks to months after corticosteroid injections and it can take even longer for the nodule and stiffness to subside. Recurrence can occur after successful injection, but is relatively uncommon.

Surgery is effective if the shealth is completely released. Recurrence after surgery is extremely uncommon. It is generally considered minor surgery and most surgeons recommend only a day or two of rest, followed by immediate and active use of the hand.

Prevention

Most people do not realize there is a problem until the swelling in the finger has built up to the point of causing mechanical disruption of the tendon glide in the tendon sheath.

Trigger finger is considered idiopathic, which is a fancy term which means the cause (or etiology) is unknown. A person who develops a trigger finger can be considered an innocent bystander. According to the best scientific understanding of this illness, there is nothing one can do to prevent it.

Speculative associations with hand use (vibratory tools, repetitive motions) and certain diseases (like diabetes and hypothyroidism) have limited scientific support to date.