Syndactyly Reconstruction

Synopsis

Syndactyly is the most common congenital hand deformity, presenting with varying levels of severity. Left untreated, syndactyly can result in hand deformity and/or failure of the hand to reach its full functional potential. Surgical treatment typically occurs within the first 2 years of life or earlier (3–6 months) in the setting of border or multiple-digit involvement. Conditions associated with syndactyly, including Apert syndrome or Poland syndrome, are common, especially in more complex cases, and should be worked up and treated appropriately. Reconstruction of syndactyly often requires use of a proximally based dorsal web space flap and interdigitating skin flaps. The use of full-thickness skin grafts permits the surgeon to cover the added circumference after release, allow for a tension-free closure, and preserve digital fat in an effort to match the size of the adjacent, unaffected fingers. Post-operative splinting and care along with long-term follow-up are important for the prevention and management of complications.

Clinical Problem

Syndactyly of the hand is defined as incomplete separation or fusion of digits. Syndactyly is typically classified based on the length of union from the web space to fingertip and on whether there is bony fusion. Simple syndactyly exists when the digit fusion consists of only a skin and soft tissue bridge. Complex syndactyly encompasses fusion of adjacent phalanges or interposition of accessory bones. Syndactyly is considered to be complete when it involves the full length of the involved digits, and incomplete when only part of the digit is involved. Complete syndactyly can also include a common fingernail, which is termed synonychia . Fusion of multiple digits is often associated with a syndrome.

Syndactyly is the most common congenital hand malformation, classified as a failure of differentiation during embryonic development. It is commonly seen in hand clinics throughout the world, including in low- and middle-income countries. During the fifth week of development, radial condensations of mesoderm within the digital plate form the fingers, which are initially joined by interdigital tissue. This interdigital tissue undergoes a planned apoptosis from distal to proximal, and by the end of the sixth week, the interdigital space is formed. Disruption in protein signaling affecting the apoptotic cascade, and consequently the separation of the digits, represents one potential mechanism in the formation of syndactyly.

The incidence of syndactyly is 3 to 10 in 10,000 births and has been reported to be as high as 10 to 40 in 10,000 births. Although syndactyly may occur sporadically, the majority of cases are inherited as autosomal dominant with variable or reduced penetrance. Other inheritance patterns include autosomal recessive and X-linked recessive, both of which tend to present with more clinically severe forms of syndactyly. Syndactyly tends to be more common in males over females, and unilateral presentation is equally as common as bilateral presentation.

The presence of syndactyly may be associated with syndromes or other conditions. Syndactyly may present with skeletal manifestations including cleft hand, symbrachydactyly, and synpolydactyly. Fourth web space syndactyly is commonly associated with oculodentodigital dysplasia, which consists of optic nerve hypoplasia, small teeth with numerous caries, and a narrow midface. Acrocephalosyndactyly is found in Apert and Pfeiffer syndromes and consists of complex multiple-digit syndactyly, craniosynostosis, and midface hypoplasia. Symbrachydactyly consists of a hypoplastic hand with short fused digits and is commonly associated with absence of the sternal head of the pectoralis major muscle in Poland syndrome. Lastly, as a result of amniotic band sequence, acrosyndactyly can occur, which consists of incomplete digit fusion with proximal sinus tracts. It is critical to identify syndromes pre-operatively to rule out cardiopulmonary or bleeding issues that may lead to significant perioperative complications.