Polydactyly.

Polydactyly of the hand is among the most common congenital anomalies of the upper extremity and encompasses a broad range of anatomic and functional presentations. It is characterized by a duplicated digit, which may occur as an isolated finding or in association with genetic syndromes. Based on the location and characteristics of the duplication, polydactyly is commonly classified as preaxial, postaxial, or central. Proper evaluation requires an understanding of limb embryology, genetic influences, and classification systems, as these factors directly inform surgical planning. Treatment strategies can range from simple excision of rudimentary digits to complex reconstruction aimed at restoring stability, alignment, mobility, and appearance. This chapter focuses on hand polydactyly, reviewing its embryologic and genetic foundations, classification systems, and approaches to surgical management. Emphasis is placed on technique selection, timing of intervention, and considerations that influence functional and aesthetic outcomes.