Failure of differentiation part I: Syndactyly.

Syndactyly is one of the two most common congenital hand anomalies, the other being polydactyly. Traditionally, syndactyly is considered simple when only skin is involved; complex when there is bone connection; complete when the web involvement includes the nail folds; incomplete or partial when the nail folds are not involved, but when the web depth is distal to its normal position; and complicated when there are multiple tissue abnormalities. This article discusses the various types of syndactyly, the current state of known genetic mechanisms, and the author's preferred surgical techniques for correction.