Summary

Trigger Finger (Stenosing Tenosynovitis) is a mismatch between the volume of the flexor tendon sheath and its contents. Thickening of the A1 Pulley (primary) prevents the tendon nodule (secondary) from gliding, causing the finger to "catch" or "lock" in flexion. It affects 2% of the population, rising to 10% in diabetics. Diagnosis is clinical: a palpable snap in the palm (not the PIP joint) and a tender nodule. Management follows a highly effective ladder: Splinting -> Steroid Injection (Curative in 60-90%) -> Surgical Release of the A1 Pulley. [1,2,3]

Key Facts

• The Problem: It is a problem of entrance. The flexors are strong enough to pull the nodule into the sheath (flexion), but the extensors are too weak to pull it out (extension).
• The Site: The A1 Pulley (Metacarpal head level). This is the only pulley that is safe to cut.
• Diabetes: Strong association. Diabetics often have multiple digits involved, respond poorly to injections (50% failure), and require surgery earlier.

Clinical Pearls

"It's in the Palm": Patients usually complain of clicking at the PIP joint (middle knuckle). This is referred sensation. You must palpate the MCP joint crease in the palm to feel the nodule snapping.

"Don't Inject the Tendon": When injecting, if the plunger pushes back (high resistance), you are intral-tendinous. Withdraw slightly. Injecting the tendon causes necrosis and rupture.

"Safe Zone": The Thumb A1 pulley is dangerous. The Radial Digital Nerve crosses it obliquely. Percutaneous release is contraindicated in the thumb; open surgery is safer.

Steps

1. Look: Finger may be locked in flexion.
2. Palpate:
   • Feel the A1 pulley (Distal Palmar Crease).
   • Tenderness: Almost always present.
   • Nodule: A hard lump moving with the tendon.
3. Move:
   • Ask patient to make a fist and open.
   • Feel the "click" or crepitus under your finger in the palm.

                  TRIGGER FINGER
                        ↓
             IS IT LOCKED (Grade 3/4)?
             ┌──────────┴──────────┐
            NO                    YES
        (Grade 1/2)           (Grade 3/4)
            ↓                      ↓
       1. SPLINTING           1. INJECTION
       2. NSAIDS             (One Attempt)
            ↓                      ↓
          FAILS?                 FAILS?
            ↓                      ↓
     STEROID INJECTION        SURGERY
     (Max 2 attempts)         (Release)
            ↓
          FAILS?
            ↓
         SURGERY

1. Splinting

• Technique: MCP Blocking Splint (prevents flexion >30°). Worn at night.
• Rationale: Prevents the nodule from engaging the pulley during sleep (when swelling peaks).
• Efficacy: 50% success in mild cases.

2. Steroid Injection

• Drug: Methylprednisolone (Depo-Medrone) + Lidocaine.
• Target: The sheath (not tendon) at A1 level.
• Efficacy:
  • Non-Diabetic: 90% cure rate.
  • Diabetic: 50% cure rate.
• Risks: Fat atrophy, skin hypopigmentation, tendon rupture (rare), infection.

1. Percutaneous Release

• Technique: Using a 19G needle to slice the pulley through the skin (under local anaesthetic). No incision.
• Pros: No scar. Quick.
• Cons: Incomplete release. Nerve injury risk.
• Contraindication: Thumb (Nerve risk), Middle finger (Proximal anatomy), Severe contracture.

2. Open Release (Gold Standard)

• Technique: Small incision in palm. Direct vision. Complete division of A1 pulley.
• Success: ~100%. Recurrence rare.
• Rehab: Immediate movement to prevent adhesions.

Sato et al. (2012) Meta-analysis

• Steroid injections are superior to splinting.
• Surgery is superior to injection for long-term cure >1 year.

Diabetic Trigger Finger (Castellanos et al.)

• Diabetics have multiple digit involvement and respond poorly to injections. Many surgeons advocate for early surgery in this group.

What is Trigger Finger?

The tendons that bend your fingers glide through a tunnel. In your case, the tunnel entrance (pulley) has thickened, or the tendon has a knot on it. It's like trying to pull a knot through a needle eye. It gets stuck, then snaps through.

Why do I have it?

It's usually age-related wear and tear. It is very common in diabetes. It's not usually from a specific injury.

Will the injection work?

For most people, one injection cures it permanently. It reduces the swelling so the knot fits through the tunnel again.

What causes the Locking?

Ideally, your muscles are strong enough to pull the knot in (making a fist), but not strong enough to push it out (opening hand). That's why you have to use your other hand to unlock it.

Q1: Which pulley is pathologically involved in Trigger Finger? A: The A1 Pulley (Annular Pulley 1) at the level of the MCP joint.

Q2: Which pulleys are critical to preserve? A: The A2 (Proximal Phalanx) and A4 (Middle Phalanx) pulleys. Loss leads to bowstringing and loss of excursion/power.

Q3: Why is percutaneous release contraindicated in the Thumb? A: The Digital Nerves of the thumb runs very close to the midline at the A1 pulley level (unlike fingers where they are more lateral). The Radial Digital Nerve is particularly at risk of transection.

Q4: What is Notta's Node? A: A nodule on the Flexor Pollicis Longus tendon seen in Congenital Trigger Thumb. It presents as a thumb fixed in flexion in an infant.

(End of Topic)