Trigger finger

(Stenosing flexor tenosynovitis)

Epidemiology

• Most common in women 40-60yo
• Higher prevalence in diabetics, arthritis, and amyloidosis

Aetiology

• Unknown
• Often attributed by patients to overuse or repetitive movements
• When seen in children, higher prevalence of anatomic variations or inherited conditions

Pathophysiology

• A disparity in size of the flexor tendons and the surrounding retinacular pulley system at the A1 pulley. The flexor tendon catches when it attempts to glide through a relatively stenotic sheath.
• Results in difficulty smoothly flexing or extending the finger, and sometimes even locking, in severe cases.
• The histopathological change is fibrocartilaginous metaplasia of the ligamentous layer of the tendon sheath at the A1 pulley, with reduction in the cross-sectional area of the fibro-osseous canal.
• Not unusual to have multiple trigger fingers
• A1 pulley is overlying MCPJ (see below)

Diagnosis

• Locking at MCPJ
• Palms up, and trial active extension and flexion to elicit locking
• Palpate over PIPJ as the finger is actively flexed and extended, to assess for clicking/catching
• The locking does not have to occur with every movement
• Locking indicates more severe disease
• XR is unnecessary in most cases

Differential diagnosis

• Dupuytren's contracture (fixed and chronic loss of full extension, at the MCPJ; painless, with nodules usually palpable in the palmar fascia)
• Diabetic cheiroarthropathy (typically affects all fingers symmetrically)
• MCPJ sprain (recent trauma)
• Infection
• RA - a snapping phenomenon can occur with flexor tendon synovial inflammation at the carpal tunnel

Indications for surgery

• Failed conservative management (activity modification, splinting in slight flexion, short-term NSAIDs)
• Not appropriate or unwilling to try one or two glucocorticoid injections
• Secondary trigger finger (to other medical condition) which is unlikely to resolve with surgical management

Contraindications

• RA - these patients should have open synovectomy and excision of intra-tendinous nodules, leaving the A1 pulley intact

Surgery

• Technique - finger
  • Wide awake, LA, no tourniquet
  • Can be transverse, longitudinal or chevron incision over the A1 pulley
  • Use Metz scissors to expose the tendon sheath with gentle spreading. Blunt ends of cats paw retractors to protect other structures/expose.
  • Take the finger through several cycles of active movement to ensure full release
  • Close the wound (4/0 Nylon or Vicryl Rapide)
  • Rehabilitation is unnecessary, unless contractures were present, but encourage finger ROM
• Technique - thumb
  • Beware of radial digital nerve of the thumb - crosses obliquely over the A1 pulley, especially proximally
• Complications
  • Recurrence 3%
  • Infection
  • Digital nerve injury
  • Flexor tendon bowstringing