Trigger Finger / Thumb Release (A1 Pulley)

Surgical Indications

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 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 with failed single injection
• Multiple digit involvement with significant functional impairment
• Suspected concomitant flexor sheath pathology (nodule, ganglion) requiring open exploration

Contraindications

Absolute:

• Active flexor sheath infection (Kanavel signs positive — requires urgent washout, not injection or pulley release)
• Uncontrolled anticoagulation in the setting of percutaneous release

Relative:

• Grade I-II triggering with no prior trial of injection (try injection first in most patients)
• Pregnancy (defer unless severe functional impairment)
• Active psoriatic or rheumatoid flare (optimise medical management first)

Evidence for Non-Operative Treatment

Corticosteroid Injection

• Short-term resolution: a single corticosteroid injection resolves symptoms in a substantial majority of idiopathic trigger digits, with reported short-term success commonly in the 60-90% range across series
• Durability: recurrence is common within 1 year, and is higher in diabetics and multi-digit disease; the Cochrane review of surgery vs injection found markedly less recurrence with open surgery (8/140 vs 50/130 at 6-12 months, RR 0.17)
• Number of injections: two injections are generally considered a reasonable maximum before offering surgery; benefit from a third injection is limited
• Technique: inject approximately 1 mL of triamcinolone acetonide 40 mg/mL (or methylprednisolone) with 0.5 mL 1% lidocaine into the flexor tendon sheath at the A1 pulley level — confirm needle is intra-sheath (not intratendinous) by observing the needle move with passive tendon excursion before injecting
• Benson and Ptaszek (1997, J Hand Surg Am, PMID 9018627): comparative review of 109 trigger fingers; supports surgical A1 pulley release as a reasonable next step after a single failed injection given the permanency of relief

NSAIDs and Splinting

• A Cochrane review (Leow 2021) found injected NSAIDs offer little to no benefit over glucocorticoid injection; glucocorticoid remains the preferred injectable
• Static splinting (e.g. MCP extension/blocking splint) reduces symptoms in mild Grade I-II disease and is a low-risk adjunct, though generally less effective than corticosteroid injection alone

Evidence for Surgery

Open vs Percutaneous Release

Open release (long-standing standard):

• High complete-release rate with low recurrence
• Direct visualisation of the neurovascular bundles — particularly valuable in the thumb
• Allows inspection and excision of associated tenosynovial pathology

Percutaneous needle release:

• High success in the index, middle and ring fingers; lower cost, faster recovery, no formal incision
• Caution in the thumb — the radial digital nerve crosses just proximal to the pulley; prefer open or ultrasound-guided release
• A meta-analysis of 8 RCTs (Casey 2024, 548 patients) found NO significant difference between open and percutaneous release in revision, complication or pain rates — both are appropriate techniques in suitable fingers

Key Evidence

Pulley System of the Flexor Tendon Sheath

Annular Pulleys (A1-A5)

The flexor tendon sheath contains five annular pulleys that prevent bowstringing and optimise mechanical efficiency of the flexor tendons.

Key principle: In trigger finger, ONLY the A1 pulley is released. The A2 pulley proximal margin must be identified and protected — inadvertent release of the A2 proximal edge risks bowstringing.

Cruciate Pulleys (C1-C3)

Oblique-fibre pulleys between the annular pulleys — can all be divided without biomechanical consequence. Not involved in triggering.

Anatomical Landmark: Surface Creases vs the A1 Pulley

• Distal palmar crease (DPC): the practical surface landmark — cadaveric work shows the finger A1 pulley begins just distal to the DPC, which overlies the metacarpal head/neck (Chung)
• Finger MCP flexion (digital) crease: lies DISTAL to the MCP joint, over the proximal phalanx (A2 region) — it is NOT the A1 pulley landmark, a common point of confusion
• Metacarpal head: palpable as the bony prominence of the knuckle in extension — a reliable bony reference for the A1 pulley level
• Thumb: the A1 pulley proximal edge lies only about 3.5 mm distal to the thumb MCP flexion crease (Buldu)
• Clinical implication: centre the incision on the distal palmar crease or palpated metacarpal head; do not rely on the digital crease, which lies distal to the joint

Neurovascular Anatomy — Finger vs Thumb

Finger Digital Nerves

• The radial and ulnar digital nerves run 4-6 mm lateral to the flexor sheath in the finger
• They run in the mid-lateral line of the digit (dorsal to the skin crease)
• At the A1 pulley level, the nerves are separated from the pulley by subcutaneous fat — relatively protected
• Risk: Aggressive blunt dissection in the subcutaneous plane; nerves displaced in scarred or previously injected tissue

Thumb Digital Nerves — Extra Hazard (technique-dependent)

• The thumb digital nerves lie much closer to the A1 pulley than finger nerves. In a cadaveric study (Buldu), the ulnar digital nerve lay a mean of 1.95 mm from the pulley and the radial digital nerve a mean of 3.40 mm
• The radial digital nerve crosses the volar surface of the flexor tendon just proximal to the A1 pulley — a percutaneous needle entering proximally/radially can encounter it before reaching the pulley
• Open release: the ULNAR digital nerve is closest to the dividing blade and is the structure most at risk
• Percutaneous release: the RADIAL digital nerve (crossing proximal to the pulley) is the structure most at risk
• Protection: identify BOTH digital nerves under direct vision before any pulley division; in the thumb, prefer open release (or ultrasound-guided percutaneous release)

Thumb — Match the Risk to the Technique

The classic teaching that the radial digital nerve is "always" the key thumb risk is an oversimplification. Cadaveric anatomy shows the ulnar digital nerve is closest to the pulley and most threatened during open division, whereas the radial digital nerve — crossing proximal to the pulley — is most threatened by a blind percutaneous needle. Awareness of both, with direct visual identification, is the safeguard.

Thumb A1 Pulley — Specific Features

• Origin: Volar plate of thumb MCP joint
• Length: 8-10 mm (slightly shorter than finger pulleys)
• FPL tendon (flexor pollicis longus) is the only tendon in the thumb flexor sheath — no FDS component
• Triggering is caused by a nodule on the FPL tendon (Notta's node in children)
• The thenar muscles are immediately radial and dorsal to the thumb A1 — protect from excessive dorsal retraction

Positioning and Preparation

Patient position: Supine, arm abducted 90 degrees on hand table, forearm supinated. No tourniquet required for WALANT technique. If tourniquet used, apply to forearm (200 mmHg) for better comfort with minimal haematoma risk.

Anaesthesia: WALANT is strongly preferred — 2-3 mL of 1% lidocaine with 1:100,000 epinephrine, injected subcutaneously 15-20 minutes before incision. Awake patient confirms resolution of triggering before skin closure.

Consent: Specifically counsel regarding risk of digital nerve injury (thumb: 0.5-2% open, higher percutaneous without US guidance), incomplete release (1-2% open), wound complications, infection (less than 1%), and scar sensitivity.

Open Technique — Step-by-Step

Step 1: Marking Incision

Flex and extend the finger to confirm triggering. Palpate the metacarpal head (bony prominence of the knuckle in extension) to confirm the A1 pulley level.

For the finger, mark a transverse incision 1-1.5 cm at the level of the distal palmar crease / palpated metacarpal head (the A1 pulley begins just distal to the distal palmar crease). Do not centre on the finger MCP flexion (digital) crease, which lies distal to the joint over the proximal phalanx. A short longitudinal/oblique incision is an acceptable alternative.

For the thumb, use a transverse or gently curved incision at the MCP flexion crease level under loupe magnification, identifying both digital nerves; a longitudinal extension can be added if more exposure is needed.

Step 2: Subcutaneous Dissection and Nerve Identification

Incise skin sharply with a number 15 blade. Deepen through subcutaneous fat using spreading scissors in line with the digit. Identify and protect subcutaneous veins.

For the finger: Identify the digital neurovascular bundles on either side (running 4-6 mm lateral to midline). Retract with skin hooks or vessel loops.

For the thumb: Carefully identify BOTH digital nerves. The radial digital nerve crosses the flexor tendon just proximal to the A1 pulley; the ulnar digital nerve lies close to the ulnar border of the pulley (cadaveric mean about 1.95 mm) and is the closest structure to the dividing blade in an open approach. Identify and protect both before any pulley division.

Step 3: Expose the A1 Pulley

Deepen dissection to the level of the A1 pulley — a distinct thickened white fibrous band with transverse fibre orientation lying over the flexor tendon. Identify the proximal and distal edges of the A1 pulley.

Confirm the A2 pulley immediately distal — mark its proximal edge with a small clip or instrument to avoid inadvertent A2 incision.

Step 4: A1 Pulley Release

Using a number 15 blade or tenotomy scissors, divide the A1 pulley longitudinally in the midline from its proximal to distal margin. The blade should advance along the pulley surface, directed away from the underlying tendon. Insert a fine elevator under the proximal margin first, then divide under direct vision.

In the thumb: divide the pulley in the midline under direct vision with both digital nerves protected. Keep the blade angled away from the ulnar border (where the ulnar nerve lies closest) and ensure the radial nerve crossing proximally is out of the cutting path before dividing.

Step 5: Verify Complete Release

With the wound open, actively flex and passively extend the digit (WALANT allows patient-confirmed active motion). Check for smooth gliding through the pulley. No snapping, catching, or triggering should be present.

If catching persists, inspect for: (1) A1 distal margin not fully released, (2) A2 proximal margin catching, (3) FDS-FDP mismatch at chiasma of Camper (rare), (4) large tenosynovial nodule requiring excision.

Step 6: Wound Closure

Close skin with 4-0 non-absorbable interrupted sutures (nylon or Prolene) in the finger. Use 4-0 absorbable sutures in children. Apply non-adherent dressing. No splint required — encourage immediate active finger motion.

Percutaneous Needle Release — Technique

Indications

• Grade II-III trigger finger (NOT thumb — contraindicated without ultrasound guidance)
• Patient preference, clinic setting, multiple digits
• Contraindicated: Grade IV fixed triggering, previous failed release, suspected tenosynovial pathology

Technique

1. Mark A1 pulley level (distal palmar crease / palpated metacarpal head — the pulley begins just distal to the distal palmar crease)
2. Infiltrate 1-2 mL WALANT subcutaneously
3. Insert 18-gauge needle through skin into the sheath at the proximal A1 margin, bevel parallel to tendon
4. Confirm intrasheath position: move needle with tendon excursion
5. With needle bevel oriented to cut the pulley (perpendicular to fibres), make 3-5 controlled sweeping cuts from proximal to distal along the pulley
6. Ask patient to actively flex and extend — confirm resolution of triggering
7. If triggering persists, advance needle to distal margin and repeat

Post-operative Protocol

Early Phase (Day 0-14)

• Immediate active mobilisation: Start active flexion and extension of the released digit from day 1 — no splinting required for trigger finger release
• Dressing: Non-adherent (Jelonet) plus light gauze; no cast or splint
• Elevation: Elevate hand above heart for first 48 hours to reduce swelling
• Analgesia: Paracetamol and NSAIDs; opioids not routinely required
• Suture removal: 10-14 days for non-absorbable sutures

Return to Function

• Light activities: From day 1-2
• Driving: When safe to grip steering wheel (usually day 2-5)
• Return to work: Office work within 1 week; manual work 2-3 weeks
• Full grip strength: By 4-6 weeks in most patients

Hand Therapy Indications

• Pre-existing PIP joint flexion contracture (Grade IV presenting feature): splinting and therapy from day 1
• Scar tenderness persisting beyond 4 weeks: scar massage, desensitisation
• Stiffness at 4-6 weeks: formal hand therapy for ROM exercises
• Diabetic patients with multiple digits: early hand therapy input recommended

Special Case: Paediatric Trigger Thumb (Notta's Node)

Epidemiology and Natural History

• Presents as a fixed (often painless) flexion deformity at the interphalangeal joint of the thumb in infants and young children
• Caused by a nodule (Notta's node) on the FPL tendon at the A1 pulley level
• Usually not present at birth — most commonly identified between 1 and 3 years of age
• Spontaneous resolution: in a prospective natural-history cohort (Hutchinson), about 32% of thumbs resolved spontaneously by 5 years with observation
• Prognostic factor: each degree of initial IP flexion reduces the chance of resolution by 3%; IP flexion contracture greater than 30 degrees resolved in only about 2.5% and favours earlier release. Bilateral involvement increases the likelihood of eventual surgery
• Recommendation: a period of observation is reasonable; offer release for persistent triggering, fixed IP contracture greater than 30 degrees, or parental preference after counselling

Surgical Technique in Children

• General anaesthesia (children)
• Transverse incision at MCP joint level (same landmark principle as adult)
• Extra care with digital nerves — smaller calibre in children (1-2 mm diameter), very close to the pulley
• Use loupe magnification (minimum 2.5x)
• Divide A1 pulley completely under direct vision; excise Notta's nodule if large
• Close skin with absorbable sutures (4-0 Vicryl rapide) — no suture removal needed
• Outcomes: Greater than 95% complete resolution of triggering

Outcomes in Paediatric Trigger Thumb

• Surgical success rate: 95-98% complete resolution
• Recurrence after surgery: less than 2%
• Normal IP joint function: restores in majority within 3-6 months post-operatively
• Bilateral involvement in 25% — both thumbs may require staged release

Special Case: Diabetic Trigger Finger

Why Diabetes Changes Management

• Synovial thickening from collagen glycosylation involves both the tendon and the sheath
• Multiple digit involvement (up to 5 digits) is common
• Corticosteroid injection: higher risk of transient glycaemia elevation (warn and monitor for 48-72 hours)
• Corticosteroid injection success at 1 year: 30-50% vs 60-80% in non-diabetics
• Recommendation: After one or two failed injections, proceed to surgery — do not delay with repeated injections in diabetics

Surgical Considerations in Diabetes

• Higher wound infection risk: consider perioperative antibiotic prophylaxis (e.g. IV cefazolin at induction; cephalexin is an oral agent, not for IV use)
• Wound healing may be delayed: sutures left in 14 days
• Neuropathy may mask postoperative pain — monitor for early signs of infection
• Staged bilateral or multiple-digit release may be needed to limit total anaesthetic risk