How To Treat Polysyndactyly And Syndactyly Of The Foot

Edwin Harris, DPM, FACFAS

Drawing on his clinical experience and the literature, this author provides a comprehensive guide to surgical approaches to the various forms of polysyndactyly and syndactyly in pediatric patients, focusing on which segment to delete and how to avoid surgical complications.

Developmental errors in digital and metatarsal formation are common pediatric anomalies. These include bone and soft tissue digital fusions, multiple digits and complex deformities involving both of these patterns. In addition, there may be associated metatarsal, midfoot and rearfoot developmental abnormalities. They may occur in isolation, be combined with deformities of the upper extremity or may be part of a cluster of skeletal and visceral malformations that constitute identifiable syndromes.

   In polydactyly, there are more than five digits on an extremity. These take the form of more or less complete duplications. In some cases, the digit is perfectly formed. In others, there may be incomplete expressions distinguished by deficient phalangeal and nail plate development. On occasion, the duplicated digits may be abnormally placed. On rare instances, radiographically recognizable phalanges can be visible in the interval between the first and second metatarsal bases in the same area as the os intermetatarseum. Polydactyly may occur in isolation or may be a component of a syndrome combined with other congenital skeletal and visceral anomalies.1-5

   Syndactyly is characterized by failure of two or more adjacent digits to segmentalize fully. A number of subsets are recognized. Simple syndactyly is defined as a complete separation of the adjacent phalanges even though they are contained in a more or less complete single skin envelope. In complete syndactyly, the fusion extends to the hyponychium.

   Incomplete syndactyly is defined as partial fusion of adjacent soft tissue segments of the toes but the level of skin fusion does not extend to the hyponychium. The presence of two distinct nail plates usually indicates two separate distal phalanges or at least duplicated terminal tufts. In complex syndactyly, the phalanges fuse together at some point along the course of the bony segments. The fusion is most likely to occur at the tips of the distal phalanges.

   Fenestration occurs very infrequently. It most likely occurs in complete syndactyly when a well-defined opening occurs between the superior and inferior aspects of the soft tissue bridge.

   Syndactyly is one of the most common occurring limb malformations. It can occur in isolation or may be a component of more than 300 syndromic anomalies.6 Syndactyly occurs in 1:2,000 to 1:2,500 live births, and is three times more common in males. The second and third toes are most frequently involved.7 Tibial (preaxial) polydactyly accounts for 15 percent of all toe duplications and fibular (postaxial) polydactyly accounts for 79 percent.8,9

   Polysyndactyly (synpolydactyly) is a variation of polydactyly in which the extra toes are contained in a single skin envelope.

   Polysyndactyly in disarray is a deformity usually associated with other named syndromes. The best examples are Carpenter and Apert syndromes. These are complex disorders involving cranial and maxillofacial abnormalities, upper extremity variations of polysyndactyly and foot deformities that include polysyndactyly and major rearfoot coalitions.

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