28. Stenosing flexor tenosynovitis (trigger finger) - etiology, pathogenesis, clinical manifestations, diagnosis, treatment, medical expertise.

Introduction

Stenosing flexor tenosynovitis, known as trigger finger (digital tenovaginitis stenosans, snapping finger), is a common cause of painful catching or locking of a finger in flexion. It is a narrowing of the fibro-osseous flexor tendon sheath at the level of the A1 (annular) pulley, most often at the metacarpophalangeal joint. It is typically linked to repetitive forceful gripping, and it is also associated with diabetes and rheumatoid arthritis. The note covers its causes, mechanism, clinical picture, diagnosis, treatment and the approach in medical expertise.

Etiology and pathogenesis

The disorder results from a mismatch between the flexor tendon and its sheath. Repeated forceful flexion and gripping cause local friction and microtrauma, which lead to a chronic inflammatory and fibrotic response. Key points:

• Occupational causes: repetitive forceful gripping, pinching and use of vibrating or heavy hand tools, in manual and assembly work.
• Non-occupational causes: diabetes mellitus, rheumatoid arthritis, hypothyroidism, gout and amyloidosis; women and patients aged about 40 to 60 are affected more often.

The pathogenetic sequence is as follows:

1. Repetitive loading causes synovial inflammation of the tendon sheath.
2. The sheath orifice at the A1 pulley thickens and narrows, which constricts the tendon.
3. The flexor tendon develops a fusiform nodule that cannot pass easily through the narrowed pulley.
4. The nodule catches on the pulley during flexion and, when it finally slips through, the finger snaps. Extension may be impaired in the same way, producing a locked finger.