TRIGGER FINGER
A1 Pulley | Stenosing Tenosynovitis | Injection | Release
Green Classification
Critical Must-Knows
- A1 Pulley: Location of stenosis at MCP level. Release A1, NOT A2.
- Ring and Middle Fingers: Most commonly affected digits.
- Steroid Injection: 70% success rate. Lower in diabetics (50%).
- A2 Pulley: CRITICAL - never release. Causes bowstringing if released.
- Diabetics: 10% prevalence, multiple digits, lower injection success.
Examiner's Pearls
- "Palpable nodule at A1 (MCP level)
- "Worse in morning (tissue edema)
- "Diabetics: 10% prevalence, multiple fingers
- "Preserve A2 = fundamental principle
Clinical Imaging
Imaging Gallery
Critical Trigger Finger Exam Points
A1 Pulley Location
Stenosis occurs at A1 pulley (MCP level). Nodule in flexor tendon catches at pulley during motion. Release A1, never A2.
Preserve A2 Pulley
A2 is critical for tendon function. Releasing A2 causes bowstringing and loss of grip. A2 and A4 are the critical pulleys.
Diabetic Trigger Finger
10% prevalence in diabetics. Multiple digits common. Injection success only 50%. May need surgery first-line.
Injection Technique
Inject into tendon SHEATH, not tendon. At A1 pulley level. 70% success. May repeat once. Avoid tendon injection.
Quick Decision Guide
| Grade | Presentation | Treatment | Key Action |
|---|---|---|---|
| Grade 1 | Pain only, no catching | Conservative, splint | Trial of splint and activity modification |
| Grade 2 | Catching, active extension OK | Injection first | 70% success with steroid injection |
| Grade 3 | Locking, passive unlock needed | Injection or surgery | Consider surgery if injection fails |
| Grade 4 | Fixed locked | Surgery | A1 pulley release indicated |
A1-A2-A3-A4-A5Annular Pulley System
Memory Hook:A2 and A4 are the CRITICAL pulleys - never release them! A1, A3, A5 are minor and can be released safely.
DRAGTrigger Finger Risk Factors
Memory Hook:DRAG = Diabetes, RA, Age 50-60, Gripping - know the risk factors for trigger finger!
SHEATHInjection Technique
Memory Hook:SHEATH = where you inject! Into the tendon sheath, not the tendon itself.
Overview and Epidemiology
Why Trigger Finger Matters
Trigger finger is extremely common in the exam. Key points: A1 pulley location, preserve A2, injection 70% success, diabetics have higher prevalence and lower injection response.
Trigger Finger (stenosing tenosynovitis) is catching or locking of a digit due to stenosis at the A1 pulley.
Demographics
- Prevalence: 2-3% general population
- Gender: Female greater than male (6:1)
- Age: Peak 50-60 years
- Digits: Ring greater than middle greater than thumb greater than index greater than small
Middle-aged women are the classic demographic.
Risk Factors
- Diabetes: 10% prevalence (vs 2% general)
- Rheumatoid arthritis: Inflammatory tenosynovitis
- Gout: Crystal-induced
- Repetitive gripping: Occupational
- Carpal tunnel: Associated conditions
Screen diabetics for trigger finger.
Pathophysiology and Mechanisms
Pulley Anatomy
There are 5 annular pulleys (A1-A5) and 3 cruciate pulleys (C1-C3). A2 and A4 are CRITICAL for tendon function - never release them. A1, A3, A5 are minor and can be safely released.
Flexor Tendon Sheath Anatomy:
- A1 Pulley: At MCP joint level - where trigger finger occurs
- A2 Pulley: Over proximal phalanx - CRITICAL, do not release
- A3 Pulley: At PIP joint level - minor
- A4 Pulley: Over middle phalanx - CRITICAL, do not release
- A5 Pulley: At DIP joint level - minor
Pathophysiology:
- Repetitive friction causes tendon sheath thickening at A1
- Nodule forms in flexor tendon (FDS or FDP)
- Nodule catches at narrowed A1 pulley
- Results in catching, triggering, or locking
Classification Systems
Green Severity Grading
| Grade | Description | Clinical Features | Treatment |
|---|---|---|---|
| Grade 1 | Pain, palpable nodule | History of catching, no demonstrable catching | Splinting, activity modification |
| Grade 2 | Catching | Demonstrable catching, can actively extend | Steroid injection (70% success) |
| Grade 3 | Locking | Requires passive extension to unlock | Injection or surgery |
| Grade 4 | Fixed locked | Unable to passively extend the digit | Surgical release indicated |
Higher grades progressively more likely to need surgery.
Clinical Assessment
History
- Catching or clicking: During flexion/extension
- Locking: May need passive unlock
- Worse in morning: Tissue edema after rest
- Pain at palm: Over MCP crease
- Progressive: Gets worse over time
Ask about diabetes and occupation.
Examination
- Palpable nodule: At A1 pulley (MCP crease)
- Tenderness: Over A1 pulley
- Triggering: Demonstrable with flexion/extension
- Grade: Can actively extend, needs passive, or fixed?
- Other fingers: Check all digits
Always palpate at the MCP crease, not PIP.
Differential Diagnosis
Consider: Dupuytren's contracture (cord, not nodule at A1), FDS/FDP anomaly (absent FDS in small finger), MCP joint pathology (arthritis, locking from loose body), tenosynovitis (RA, infection).
Investigations
Investigation Protocol
Clinical diagnosis in most cases. Palpable nodule at A1 with triggering is pathognomonic. No imaging needed routinely.
HbA1c or fasting glucose if not known diabetic. Diabetics have 10% trigger finger prevalence and need careful counseling about lower injection success.
Rarely required. Can show tendon sheath thickening, A1 pulley thickening, tendon nodule. Useful if diagnosis uncertain.
No imaging is required for typical trigger finger with clear clinical findings.
Management Algorithm
Non-Operative Management
Conservative Options
Reduce gripping activities. Especially repetitive gripping. Modify work tasks if occupational.
Night splint keeping MCP in extension. Prevents tendon nodule catching overnight. Variable success.
Short-term anti-inflammatory. May reduce symptoms but won't resolve stenosis.
Conservative treatment has limited long-term success as sole treatment.
Surgical Technique
Open A1 Pulley Release
Surgical Steps
Local anesthesia. Wide-awake local anesthesia no tourniquet (WALANT) preferred. Hand on table.
Transverse incision at MCP crease. 1-1.5cm. Follow skin crease for cosmesis.
Blunt spread to expose A1 pulley. Identify and protect digital nerves (lateral).
Incise A1 pulley longitudinally. Divide completely. STOP at A2.
Test tendon excursion. Ask patient to flex/extend. Confirm no triggering.
Skin only. Interrupted sutures or steri-strips. Soft dressing.
Simple, quick procedure (less than 10 minutes). LA suitable.
Complications
Complications of Trigger Finger Treatment
| Complication | Incidence | Prevention/Management |
|---|---|---|
| Incomplete release | 5% | Ensure complete A1 division, check glide |
| Digital nerve injury | Less than 1% | Direct vision, stay central, protect nerves |
| Bowstringing | Rare | NEVER release A2 - critical pulley |
| Infection | Less than 1% | Sterile technique |
| Stiffness | 5% | Early motion, hand therapy if needed |
| Recurrence | Less than 3% | Complete release, address underlying disease |
A2 pulley injury causing bowstringing is a serious complication. Prevention is key - know anatomy.
Postoperative Care
Postoperative Protocol
Soft dressing. Immediate finger ROM encouraged. No splint needed.
Active and passive ROM. Full motion as tolerated. Keep wound dry.
Remove sutures. Most patients fully functional by this point. Scar massage.
Return to all activities. Including gripping and lifting. Scar tenderness may persist.
Return to work: Light duties immediately. Full duties 2-4 weeks.
Outcomes and Prognosis
Success Rates:
- Conservative (splint): Variable (30-40%)
- Injection: 70% (lower in diabetics - 50%)
- Surgery: 95-100%
Prognostic Factors:
| Factor | Better Outcome | Worse Outcome |
|---|---|---|
| Duration | Short (under 6 months) | Long (over 1 year), fixed locked |
| Diabetes | Non-diabetic | Diabetic (50% injection success) |
| Grade | Lower grade | Higher grade (4 = surgery) |
| Digits | Single digit | Multiple digits |
Most patients do very well with injection or surgery.
Evidence Base
- Steroid injection effective vs placebo
- 70% success rate with single injection
- Multiple injections may improve outcomes
- Limited high-quality evidence for splinting
- Open vs percutaneous release
- Similar success rates (greater than 95%)
- Percutaneous higher recurrence in some studies
- Open provides direct visualization
- Diabetics have 10% trigger finger prevalence
- Multiple digits common in diabetics
- 50% injection success (vs 70% non-diabetic)
- May need surgery as first-line
- A1 pulley release technique
- 97% complete resolution
- Low complication rate
- Outpatient procedure effective
- Comparison of injection vs surgery
- Injection 57% long-term success
- Surgery greater than 95% success
- Surgery more cost-effective if injection fails
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Classic Trigger Finger
"A 55-year-old woman has catching in her ring finger for 2 months. She feels a click at the palm and sometimes needs to straighten the finger with her other hand. There is a tender nodule at the MCP crease. What is your management?"
Scenario 2: Diabetic with Multiple Triggers
"A 60-year-old diabetic man has triggering in his ring, middle, and index fingers. He has had one injection to each finger with only partial improvement. What is your approach?"
Scenario 3: Fixed Locked Finger
"A 70-year-old woman presents with her middle finger locked in flexion for 2 weeks. She cannot straighten it actively or passively. Her MCP is tender. What is your management?"
MCQ Practice Points
A1 Pulley Location
Q: At what level does trigger finger occur? A: A1 pulley at the MCP joint level. This is where the stenosis and nodule catching occurs.
Critical Pulley
Q: Which pulley must be preserved during trigger finger release? A: A2 pulley. A2 and A4 are critical for tendon function. Releasing A2 causes bowstringing.
Injection Success
Q: What is the success rate of steroid injection for trigger finger? A: 70% in general population. Only 50% in diabetics.
Diabetes Prevalence
Q: What is the prevalence of trigger finger in diabetics? A: 10% (vs 2-3% general population). Multiple digits common. Lower injection success.
Most Common Digit
Q: Which digit is most commonly affected in trigger finger? A: Ring finger (30%), followed by middle (25%), thumb (20%), index (15%), small (10%).
WALANT Technique
Q: What is WALANT and why is it ideal for trigger finger release? A: Wide Awake Local Anesthesia No Tourniquet. Allows patient to actively flex/extend to confirm complete release and resolution of triggering.
Australian Context
Australian Guidelines:
- RACS supports injection as first-line for Grades 1-3
- Surgery indicated for Grade 4 or failed injections
- Medicare rebates available for injection (item 30206) and release (item 30070)
Medicolegal Considerations:
- Document grade and prior treatment
- Consent: discuss nerve injury, incomplete release, bowstringing
- Document diabetes status and counseling about lower success
PBS/Prescribing:
- Corticosteroid injections are not PBS-restricted
- Triamcinolone, methylprednisolone commonly used
- Can be performed in rooms or operating theater
Australian surgeons should document comprehensive consent including A2 preservation.
TRIGGER FINGER
High-Yield Exam Summary
Pathology
- •Stenosing tenosynovitis at A1 pulley
- •Ring greater than middle most common
- •Nodule catches at narrowed pulley
- •Diabetics: 10% prevalence
Clinical
- •Catching/locking with flexion
- •Worse in morning
- •Palpable nodule at MCP crease
- •Tender at A1 pulley
Green Classification
- •1: Pain, no catching
- •2: Catching, active extension
- •3: Locking, passive unlock
- •4: Fixed locked = surgery
Treatment
- •Injection: 70% success (50% diabetics)
- •Surgery: 95%+ success
- •Grade 4 = surgery first-line
- •Can repeat injection once if partial response
Surgical Principle
- •Release A1 pulley completely
- •PRESERVE A2 pulley (critical)
- •Check tendon glide
- •Protect digital nerves (lateral)
Key Points
- •A2 and A4 = critical pulleys
- •Diabetics: 10% prevalence
- •Ring finger most common
- •Multiple digits in diabetics