What is the pathophysiology of trigger finger and what is the recommended clinical approach for its management?

Trigger Finger: Pathophysiology and Clinical Approach

Pathophysiology

Trigger finger results from a stenotic A1 pulley that has lost its gliding surface, producing friction and nodular changes in the flexor tendon. 1, 2

• The condition represents a stenosing flexor tenosynovitis caused by a size mismatch between the flexor tendon and the first annular (A1) pulley 3, 2
• Progressive inflammation and narrowing of the A1 pulley leads to mechanical catching as the tendon nodule attempts to pass through the constricted pulley during finger flexion and extension 4
• The pathological sequence progresses from initial pain and tenderness over the A1 pulley, to catching during finger motion, and ultimately to complete locking of the digit 1

Clinical Presentation

Look specifically for tenderness to palpation directly over the A1 pulley at the metacarpophalangeal joint level, accompanied by painful clicking or locking during active finger flexion. 1, 4

• Patients typically present in the fifth to sixth decade of life, with higher incidence in women and diabetic patients 4
• The diagnosis is clinical: patients report clicking, catching, or frank locking of the affected digit 4
• Physical examination reveals a palpable nodule in the flexor tendon and reproduction of triggering with active finger motion 2
• Exclude fracture, tumor, or other traumatic soft tissue injuries through history and examination 4

Treatment Algorithm

First-Line Conservative Management

Begin with splinting for 6 to 9 weeks, which produces gradual improvement in most patients. 1

• Activity modification to reduce repetitive gripping motions should be implemented immediately 3, 2
• Splinting maintains the metacarpophalangeal joint in slight flexion (10-15 degrees) to prevent triggering while allowing interphalangeal joint motion 3
• Conservative measures are appropriate for mild symptoms of short duration 4

Second-Line: Corticosteroid Injection

Corticosteroid injection into the flexor tendon sheath is the definitive first-line intervention, resulting in resolution of pain within days and resolution of catching or locking within a few weeks. 1

• This is a safe, simple procedure that is curative in most cases and should be offered by primary care providers 1
• Inject into the tendon sheath at the level of the A1 pulley, avoiding direct injection into the tendon itself 1
• Single injection success rates are high in non-diabetic patients 2

Third-Line: Surgical Release

Reserve percutaneous or open A1 pulley release for injection failures, particularly in high-risk patients including diabetics and those with multiple trigger fingers. 1, 3

• Open A1 pulley release is the gold standard surgical procedure with predictable success 3, 2
• Percutaneous A1 pulley release is an alternative minimally invasive option 3, 2
• For persistent triggering despite A1 release, excision of a slip of the flexor digitorum superficialis may be required 3
• Surgical complications are rare but include bowstringing, digital nerve injury, and continued triggering 2

Special Populations

Diabetic Patients

Diabetic patients are less responsive to conservative measures and corticosteroid injections, requiring earlier consideration of surgical release. 2

• Multiple trigger fingers in diabetic patients predict higher failure rates with injection therapy 1, 2

Pediatric Trigger Thumb

Pediatric trigger thumb is treated definitively with open A1 pulley release. 3

• Unlike adults, conservative management is less effective in children 3
• Pediatric trigger finger (non-thumb digits) may require flexor digitorum superficialis excision if triggering persists after A1 release 3

Rheumatoid Arthritis

Patients with rheumatoid arthritis require tenosynovectomy instead of simple A1 pulley release. 2

• The underlying inflammatory tenosynovitis necessitates a different surgical approach than idiopathic trigger finger 2

Common Pitfalls

• Do not inject corticosteroid directly into the tendon, as this increases risk of tendon rupture; inject into the tendon sheath 1, 2
• Do not delay surgical referral in diabetic patients with failed initial injection, as they have lower success rates with repeated conservative treatment 1, 2
• Do not perform isolated A1 pulley release in rheumatoid patients, as the underlying tenosynovitis will cause recurrence 2