Trigger digit (also known as trigger thumb and trigger finger) occurs when the affected digit or digits get stuck in a bent position when gripping, like a trigger suddenly giving way when squeezed. In early cases that are less severe, pain in the palm or digit may be the only symptom with the possibility of accompanying swelling or stiffness. Overall grip strength in the affected hand may be diminished, as well.
Triggering is caused by the irritation or inflammation of the lining of the flexor tendons in the palm. Flexor tendons are cord-like, extending from the forearm muscles and pulling on the bones of the hand and digits, causing them to bend. Stretched along the palm side of the finger and thumb bones, these flexor tendons are encased in sheaths, or tubes, of firm connective tissue that form multiple bands encircling the tendons like belt loops. When the lining between a tendon and its sheath is inflamed, extra friction builds as the tendon glides along the sheath.
The tendon may get caught on the first part of its sheath when any of the following occurs:
- The normally filmy, lubricating tendon lining becomes irritated and thickens
- A bump or nodule on the tendon forms
- The first part of the sheath, which is called a pulley, thickens
- A combination of these three occurs
This catch occurs in the palm near the base of the finger or thumb, where it is usually the most painful; however, the triggering is seen or felt further along the affected digit.
In severe cases, the swelling causes the irritated tendon to get stuck so that it can’t glide. The digit can even become locked so that it can’t be straightened or bent easily without assistance from the other hand.
Signs and symptoms of trigger digit include the following:
- Finger or thumb movement creates a snapping, popping, or catching sensation
- Soreness or pain occur at the palmar base of the digit
- Bending the finger or thumb results in pain or stiffness, which is often worse upon awakening from sleep
- The digit cannot bend or straighten completely
- Swelling appears in the digit or at the palmar base of the digit
- The digit locks to the point of immobility in severe cases
- Pain in the palm occurs when the affected digit is quickly straightened or forced backward
While trigger digit can occur in newborns and infants, especially in their thumbs, trigger digit typically occurs in the following:
- Adults whose daily activities involve forceful, frequent, or sustained gripping
- Diabetic patients, who are more susceptible to multiple digits being affected simultaneously
Treatments for mild cases of trigger digit are non-invasive:
- For the affected digit, increased rest or limited activity is sometimes sufficient
- Finger stretches can help when small hand muscles tighten up after the finger catches
- Comfortable, padded finger splints can prevent triggering or locking during sleeping hours
- When symptoms have been present less than a few months, anti-inflammatory medications or steroid injections may help considerably
When symptoms have been present for many months, or if they have not responded to non-surgical treatments, surgery may be necessary. Only local anesthetic is used during the procedure, which involves cutting the thickened sheath. The triggering immediately stops and should not return because the opening of the sheath sufficiently widens as it heals. After a few weeks, full use of the digit returns; however, sometimes the finger joints themselves become stiff, and these severe cases require longer recovery periods.
- American Society for Surgery of the Hand
- American Academy of Orthopaedic Surgeons