Trigger Finger / Thumb Release (A1 Pulley)

Indication. Symptomatic trigger finger or thumb — painful catching or locking at the MCP level, tenderness over the A1 pulley at the metacarpal head, and reproduction of triggering on flexion and extension — after a fair trial of non-operative treatment. Surgery is offered for a Grade IV trigger (fixed flexion not passively reducible), failure or recurrence after two corticosteroid injections, recurrence within 6 months of a second injection, or a paediatric trigger thumb persisting beyond around 3 years of age. Absolute indications

• Grade IV trigger (locked digit in fixed flexion, not passively reducible)
• Failed conservative treatment after two corticosteroid injections
• Recurrence within 6 months of a second injection
• Paediatric trigger thumb persisting beyond 3 years of age (Notta's node) Relative indications
• Patient preference for definitive treatment over repeat injections
• Grade III triggering after a failed single injection
• Multiple digit involvement with significant functional impairment
• Suspected concomitant flexor sheath pathology (nodule, ganglion) needing open exploration Contraindications. Absolute: an active flexor sheath infection (Kanavel signs positive — this needs urgent washout, never an injection or pulley release) and uncontrolled anticoagulation in the setting of a percutaneous release. Relative: Grade I to II triggering with no prior trial of injection (try injection first), pregnancy (defer unless severe), and an active psoriatic or rheumatoid flare (optimise medical management first). Try non-operative treatment first. A corticosteroid injection resolves symptoms in roughly 60 to 90 percent of trigger digits in the short term, but recurrence is common within a year and is higher in diabetics and multi-digit disease; two injections are a reasonable maximum before offering surgery, and a third adds little benefit. The standard technique is about 1 mL of triamcinolone acetonide 40 mg/mL (or methylprednisolone) with 0.5 mL of 1 percent lidocaine injected into the flexor tendon sheath at the A1 level — confirm the needle is intra-sheath and not intratendinous by watching it move with passive tendon excursion before injecting. A Cochrane review (Leow 2021) found injected NSAIDs offer little benefit over glucocorticoid, and a static MCP extension or blocking splint is a low-risk adjunct for mild Grade I to II disease but is generally less effective than injection alone. Open or percutaneous? Both are appropriate in a suitable finger. The choice is guided by the digit, the setting and surgeon preference:

Consent. Counsel specifically on digital nerve injury (less than 0.1 percent for an open finger, 0.5 to 2 percent for an open thumb, and higher for a percutaneous thumb without ultrasound), incomplete release (1 to 2 percent open), wound infection (less than 1 percent), scar sensitivity, and a temporary 10 to 25 percent grip-strength reduction that recovers over 3 to 6 months. Setup. Supine with the arm abducted 90 degrees on a hand table and the forearm supinated. WALANT is strongly preferred — 2 to 3 mL of 1 percent lidocaine with 1:100,000 epinephrine injected subcutaneously 15 to 20 minutes before incision; no tourniquet is required, but if one is used a forearm tourniquet at 200 mmHg is more comfortable. The awake patient confirms resolution of the triggering by active flexion before skin closure.

The goal is to divide the thickened A1 pulley completely from its proximal to distal margin while protecting the flanking digital nerves and the underlying flexor tendon, then confirm smooth tendon gliding before closure. The exposure is laid out in full in the steps below.

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Percutaneous needle release Indications. A Grade II to III trigger finger (not the thumb without ultrasound), patient preference, a clinic setting, or multiple digits. Avoid it in Grade IV fixed triggering, a previous failed release, or suspected tenosynovial pathology. Technique

1. Mark the A1 level at the distal palmar crease or palpated metacarpal head.
2. Infiltrate 1 to 2 mL of WALANT subcutaneously.
3. Insert an 18-gauge needle through the skin into the sheath at the proximal A1 margin, bevel parallel to the tendon.
4. Confirm intrasheath position — the needle moves with tendon excursion.
5. Rotate the bevel to cut perpendicular to the transverse pulley fibres and make 3 to 5 controlled sweeping cuts from proximal to distal.
6. Ask the patient to actively flex and extend — confirm resolution of triggering; if it persists, advance to the distal margin and repeat.

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Rehabilitation | Phase | Timing | Management | |-------|--------|-----------| | Immediate | Day 0 to 2 | Non-adherent dressing, no splint; elevate above the heart for 48 hours; begin active flexion and extension of the released digit from day 1 | | Early | Day 2 to 14 | Light activities and driving when a safe grip is possible; paracetamol or NSAIDs (opioids rarely needed); sutures out at 10 to 14 days | | Return to function | 1 to 6 weeks | Office work within 1 week, manual work 2 to 3 weeks; full grip strength by 4 to 6 weeks | | Hand therapy | As indicated | Pre-existing PIP flexion contracture, scar tenderness beyond 4 weeks, stiffness at 4 to 6 weeks, or diabetic multi-digit disease | Grip strength is reduced by 10 to 25 percent for up to 3 to 4 months after open release and returns to baseline in most patients by 3 to 6 months — explain this before surgery. Most patients return to desk work within a week and to manual work by 2 to 3 weeks. Complications

Epidemiology and risk factors. Trigger finger is a common stenosing flexor tenosynovitis, most frequent in middle-aged women with a peak between 40 and 60 years, and strongly associated with diabetes mellitus, hypothyroidism, rheumatoid arthritis and renal dialysis. Diabetic patients are affected far more often than the general population and frequently have multiple digit involvement (up to 4 to 5 digits). Pathoanatomy. A size mismatch develops between a thickened, nodular flexor tendon (FDS and FDP in the fingers; FPL alone in the thumb) and a thickened, stenotic A1 pulley, producing catching and then locking at the MCP level. The tendon nodule is termed Notta's node in children. Histology of the A1 pulley correlates with the clinical grade (Drossos), showing fibrocartilaginous metaplasia rather than pure inflammation.

Pulley anatomy (reference). The flexor tendon sheath contains five annular and three cruciate pulleys. In trigger finger ONLY the A1 is released; the A2 and A4 are critical and must be preserved, and the cruciate pulleys can all be divided without biomechanical consequence.

Neurovascular anatomy (reference). In the finger the digital nerves run 4 to 6 mm lateral to the sheath in the mid-lateral line and are relatively protected at the A1 level. In the thumb they are far closer: the ulnar digital nerve a mean of 1.95 mm and the radial 3.40 mm from the pulley (Buldu), and the radial nerve crosses the flexor tendon just proximal to the A1. This is why the at-risk nerve in the thumb depends on the technique — ulnar in an open release, radial in a percutaneous release. Key evidence. The Cochrane review (Fiorini 2018, 14 trials, 1260 participants) found open surgery had markedly lower recurrence than corticosteroid injection (8/140 vs 50/130 at 6 to 12 months, RR 0.17) at the cost of more early palmar pain. A meta-analysis of 8 RCTs (Casey 2024, 548 patients) found no significant difference between open and percutaneous A1 release in revision, complication or pain rates, so both are appropriate in suitable fingers. Benson and Ptaszek (1997) supported proceeding to surgery after a failed injection given the permanency of relief, and Hutchinson (2021) established the natural history of paediatric trigger thumb — about 32 percent resolve spontaneously by 5 years, but an IP contracture greater than 30 degrees rarely does.