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Introduction
  • A congential malformation of the hand
  • Three forms exist
    • preaxial polydactlyly 
      • thumb duplication 
    • postaxial polydactlyly
      • small finger duplication
    • central polydactlyly
Preaxial Polydactyly (Thumb Duplication)
  • Epidemiology
    • incidence
      • 1 per 1,000 to 10,000 live births 
      • Type IV most common (43%) 
      • Type II second most common (15%)
    • demographics
      • M>F
      • caucasian > African Americans
  • Genetics
    • inheritance pattern
      • usually unilateral and sporadic 
      • except for Type VII which is associated with several syndrome including
        • Holt-Oram syndrome
        • Fanconi's anemia
        • Blackfan-Diamond anemia
        • imperforate anus
        • cleft palate
        • tibial defects
  • Associated conditions
    • pollex abductus
      • abnormal connection between EPL and FPL tendons, seen in approximately 20% of hypoplastic and duplicated thumbs
      • suggested by abduction of affected digit + absence of IP joint crease
  • Classification
 Wassel Classification of Preaxial Polydactyly 
Type I Bifid distal phalanx   
Type II Duplicated distal phalanx                            
Type III Bifid proximal phalanx                                
Type IV Duplicated proximal phalanx (most common)  
Type V Bifid metacarpal  
Type VI Duplicated metacarpal  
Type VII Triphalangia  

  • Treatment
    • operative
      • goals of treatment
        • to construct a thumb that is 80% of the size of the contralateral thumb
        • resect smaller thumb (usually radial component)
        • preserve / reconstruct medial collateral structures in order to preserve pinch function
        • reconstruction of all components typically done in one procedure
      • type 1 combination procedure (Bilhaut-Cloquet)   
        • indications
          • type I, II, or III
        • technique
          • involves removing central tissue and combining both digits into one
        • outcomes
          • approximately 20% have late deformity
          • problems include stiffness, angular and size deformity, growth arrest, and nail deformities
      • type 2 combination procedure
        • indications
          • usually favored approach for type III and IV
          • type V and VI usually require more complex transfer of intrinsics and collateral ligaments
        • technique
          • preserve skeleton and nail of one component and augment with soft tissue from other digit and ablation of lesser digit (radial digit most commonly)
      • type 3 combination procedure
        • indications
          • when one digit has superior proximal component and one digit has superior distal fragment (type V, VI, and VII)
        • technique
          • a segmental distal transfer (on-top plasty)
Postaxial Polydactyly (Small Finger Duplication)
  • Epidemiology
    • demographics
      • 10X more common in African Americans
  • Genetics
    • inherited as autosomal dominant (AD) in African Americans
    • more complex genetics in caucasians and a thorough genetic workup should be performed  
  • Classification
    • Type A - well formed digit
    • Type B - rudimentary skin tag (vestigial digits)
  • Treatment
    • operative
      • formal reconstruction with a Type 2 combination
        • indications
          • Type A
        • technique
          • preserve radial digit
          • preserve or reconstruct collateral ligaments from ulnar digit remnant
          • preserve muscles
      • tie off in nursery or amputate before 1 year of age
        • indications
          • Type B
Central Polydactyly
  • Epidemiology
    • commonly associated with syndactyly 
      • extra digit may lead to angular deformity or impaired motion
  • Treatment
    • osteotomy and ligament reconstructions
      • indications
        • perform early to prevent angular growth deformities
 

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