A trigger finger is a type of stenosing tenosynovitis. It develops due to repetitive microinjury from frequent flexion-extension movements of the fingers - professional requirement or requirement of a sports activity. The repetitive microtrauma results in thickening of the flexor tendon sheath and tendon and sometimes the A1 pulley, which leads to stenosing tenosynovitis of the flexor tendons.
A patient with trigger finger finds it difficult to straighten or bend the affected finger. The finger transiently gets locked in the flexed position and then with a painful snapping sensation goes into extension.
Ultrasonography findings include - 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.
The condition can be conservatively managed with splinting, NSAIDs and local steroid injections along with alteration in the patient's causative activity or may require surgical section of the A1 pulley when the pulley is markedly thickened.
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