What Causes Trigger Finger and How to Treat It?

Trigger finger is when a tendon in a finger becomes inflamed and can get stuck in the bent (flexed) position, like after pulling a trigger. In addition, an audible snap or pop can be heard when the finger moves back and forth. Trigger finger can occur at any of the fingers but most commonly affects the 4th finger and thumb.

Key takeaways:
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    Trigger finger causes the finger to be in a bent position, similar to pulling a “trigger.”
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    Trigger finger is caused by inflammation or a nodule of the flexor tendon not allowing smooth movement through the tendon sheath (covering).
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    Trigger finger is most commonly caused by occupations or hobbies that require repeated forceful grasping.
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    A steroid injection or surgery may be needed if conservative treatment is unsuccessful.

What is the finger anatomy involved with the trigger finger?

TRIGGER FINGER

As shown in Diagram 1, the finger’s flexor tendon enables the finger to bend, with the part of the tendon that goes under the metacarpophalangeal (MCP) joint being the A1 pulley.

trigger finger

Tendon sheaths surround the flexor tendons, shown in Diagram 1 and Diagram 2, but only labeled in Diagram 2.

During normal movement of the finger, it bends by the flexor tendons and straightens by the extensor tendons. The A1 pulley moves toward the base of the hand during finger flexion and then to the outer part of the hand during straightening.

If there is inflammation at the A1 pulley flexor tendon, the finger becomes stuck in flexion, requiring a forceful extension of the finger to "snap" it back in place. An example of this occurs when a tendon nodule is present, as shown in the top diagram. In addition, the yellow "lightning bolts" on the right side of the lower diagram reference the friction during bending (flexion) when inflammation is present.

As mentioned in the introduction, the most common fingers for trigger fingers are the thumb and the 4th finger. Note the 4th finger is also known as the ring finger in the United States; it is the finger between the middle finger and the little finger (pinky).

What causes a trigger finger?

The most common cause of the trigger finger is repetitive and forceful use of the finger, especially with firm grasping; thus, people with certain hobbies and occupations requiring this use are most likely to develop a trigger finger.

In addition, systemic diseases are associated with the trigger finger, including diabetes, gout, rheumatoid arthritis, and thyroid disease.

Lastly, having previous surgery on the hand or wrist, such as carpal tunnel syndrome surgery, can predispose a person to develop a trigger finger, especially within six months of the surgery.

What are the symptoms of a trigger finger?

The main symptoms are flexion, pain, and stiffness at the finger joint. Additional finger symptoms include snapping, popping, and soreness, especially with grasping. Sometimes, a trigger finger can go from a bent position to suddenly popping and becoming straight.

How is the diagnosis of the trigger finger made?

A history is taken to learn about occupations and hobbies, especially those requiring repetitive hand use and firm grasping. It is important to tell your physician if your finger gets stuck in a bent position or if you experience friction with finger movement.

The physical exam evaluates for any nodules or tenderness along the flexor tendons located on the palm side of the hand. The fingers should be flexed (bent) and then extended (straightened) to see if there is a smooth or rough motion, along with any elicited pain.

The joint color and temperature should be checked to evaluate for infection, which produces a red and warm joint.

Laboratory tests can check for infection, diabetes, gout, rheumatoid arthritis, and thyroid disease.

An ultrasound is a typical first-line imaging study since it can show inflammation of the flexor tendon, including the A1 pulley. In addition, an ultrasound can show real-time images of the flexor tendon movement.

Plain x-rays should be done to evaluate the bones for fractures, osteoporosis (bone thinning), or spurs (prominent bony areas at the end of bones).

The x-rays show bones but not soft tissues such as tendons, ligaments, nerves, or cartilage. Therefore, a computer tomography (CT or CAT) scan or magnetic resonance imaging (MRI) scan needs to be done to visualize the soft tissues.

Joint aspiration involves the physician placing a needle into the joint to remove fluid for evaluation, usually reserved for cases with swelling at the joint. When gout is present, uric acid crystals will be seen under a microscope, while white blood cells (WBCs) and microorganisms can be seen with infection.

What is the treatment for the trigger finger?

The first line of treatment is to avoid any activity that could be causing the trigger finger. In addition, there should be splinting of the finger in a straightened position to prevent movement of the A1 tendon; thus, minimizing irritation and inflammation.

Anti-inflammatory medications can be beneficial. These include ibuprofen (Advil), naproxen (Aleve), Celebrex, and others.

Exercises to stretch the tendon can help.

A steroid injection directly into the tendon sheath is usually helpful. These injections are inexpensive, easily performed, and not as invasive as a surgical procedure. However, some patients require repeat injections, and full recovery may take several months.

Percutaneous release involves using an ultrasound-guided needle to break up the inflamed synovial sheet surrounding the involved tendon.

Surgery involves directly cutting the A1 tendon sheath to allow normal function of the tendon.

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