Updated: 3/8/2017

Congenital Trigger Thumb

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Introduction
  • Pediatric condition of the thumb that results in abnormal flexion at interphalangeal (IP) joint
  • Epidemiology
    • prevalence
      • 3 per 1,000 children are diagnosed by the age of 1 years 
    • demographics
      • separate entity to adult acquired trigger thumb
      • male and females affected equally
    • location
      • 25% are bilateral
    • risk factors
      • etiology of pediatric trigger thumb remains unknown
  • Pathophysiology
    • pathoanatomy
      • flexor pollicis longus (FPL) tendon is thickened due to abnormal collagen degeneration and synovial proliferation
      • increased FPL tendon diameter, compared to the A1 pulley, causes disruption of normal tendon gliding
  • Genetics
    • most commonly an acquired condition
    • some reports suggest autosomal dominance with variable penetration
    • term congenital trigger thumb is now considered a misnomer
  • Prognosis
    • natural history
      • usually begins with notable thumb triggering that progresses to a fixed contracture
      • spontaneous resolution unlikely after age of 2 years old
Presentation
  • History
    • presenting complaint is usually fixed thumb flexion deformity at the IP joint
    • history of trauma is rare
    • family history of disease is rare
  • Symptoms
    • usually painless
    • may be bilateral
  • Physical exam
    • inspection
      • flexion deformity at the IP joint 
    • motion
      • prominence of the flexor tendon nodule, referred to as "Notta's node"
      • deformity may be fixed with loss of IP joint extension
    • neurovascular 
      • usually preserved
Imaging
  • Radiographs
    • recommended views
      • AP and lateral views of the hand
    • additional views
      • dedicated thumb views
    • indications
      • recommended only if history of trauma
    • findings
      • usually diagnosed based on clinical presentation
      • radiographs are usually normal
Treatment
  • Nonoperative 
    • passive extension exercises and observation
      • indications
        • not recommended for fixed deformities in older children
      • technique
        • passive thumb extension exercises
        • duration based on clinical response
      • outcomes
        • 30-60% will resolve spontaneously before the age of 2 years old
        • <10% will resolve spontaneously after 2 years old
    • intermittent extension splinting
      • indications
        • first line of treatment
          • more successful than observation alone
        • consider alongside stretching regime
        • flexible deformity
          • not recommended with fixed deformity in older children
      • technique
        • splints maintain IP joint hyperextension and prevent MCP joint hyperextension
        • duration for 6-12 weeks
      • outcomes
        • 50-60% resolution in all age groups
        • high drop out rate from therapy
  • Operative
    • A1 pulley release   
      • indications
        • fixed deformity beyond age of 12 months of age
        • failed conservative treatment
      • outcomes
        • 65-95% resolution in all age groups
Techniques
  • A1 Pulley Release
    • open release
      • small transverse incision in the thumb MCP flexion crease, extending over the A1 pulley
      • protect the radial digital nerve
      • sharp dissection of the A1 pulley
      • identify the Notta nodule in the FPL tendon
      • watch nodule under direct vision during passive IP extension of the thumb to ensure there is smooth FPL tendon gliding
Complications
  • Digital nerve injury
    • caution must be performed during release as digital nerves at high risk due to proximity to flexor tendon and A1 pulley
  • Wound complications
    • scar contracture
    • abscess
    • infection
  • IP flexion deficit
  • Bow-stringing of flexor tendon
    • usually related to release of the oblique pulley
 

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