summary Polydactyly of Hand is a congenital malformation of the hand that presents with an extra digit in the hand. Diagnosis is made clinically. Treatment is usually a form of surgical reconstruction depending on the level of duplication and the specific digit involved. Etiology Forms 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 syndromes 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 thorough genetic workup should be performed to evaluate for chondroectodermal dysplasia or Ellis-van Creveld syndrome 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