Trigger fingers are a type of stenosing tenosynovitis involving the flexor digitorum superficialis at the level of the A1 pulley. It develops due to repetitive microinjury from frequent flexion-extension movements of the fingers and/or thumb.

Epidemiology

Risk factors

• diabetes

• obesity

• female gender

• occupations with high hand activity ⁵

Clinical presentation

Patients with trigger finger or trigger thumb find it difficult to straighten or bend the affected digit. The digit transiently gets locked in the flexed position and with a painful snapping sensation going into extension.

Pathology

Repetitive microtrauma results in thickening of the flexor tendon sheath and tendon, and sometimes the A1 pulley, which leads to stenosing tenosynovitis of the affected flexor tendon.

Etiology

• idiopathic (most common)

• rheumatoid arthritis

• tumor

• connective tissue disease ⁵

Radiographic features

Ultrasound

Thickening of the A1 pulley that overlies the metacarpal heads and alteration in echotexture of the flexor tendons that pass through the digital tunnel. There may be synovial sheath effusion around the tendons. The level of thickening can be variable with some authors suggesting the normal value being around 0.5 mm with thickening suggested when the diameter is over 1.1 mm ³.

Treatment and prognosis

The condition can be conservatively managed with splinting and NSAIDs, along with an alteration in the patient's causative activity. Ultrasound-guided corticosteroid injection can be performed to reduce inflammation. Surgical intervention may be required of the A1 pulley if the pulley is markedly thickened despite less invasive management.