Classification of Postaxial Polydactyly of the Foot

Abstract

Background: The origins and shapes of accessory digits in postaxial polydactyly of the foot were analyzed morphologically and radiographically, and their characteristics were determined. A simple classification method was then devised to assist in determining the most appropriate treatment options. Methods: We evaluated 113 feet of 95 patients who had surgery for the treatment of postaxial polydactyly between 1998 and 2002. Based on the morphologic, radiographic, and operative findings, the cases were classified according to the origin of the accessory digit: middle phalangeal, proximal phalangeal, floating, fifth metatarsal, or fourth metatarsal. The proximal phalangeal type was further divided into three subtypes: proximal phalangeal lateral type, proximal phalangeal medial, and proximal phalangeal head. Results: Of the 113 feet, 36 were middle phalangeal type, 45 were proximal phalangeal type, 5 were floating type, 15 were fifth metatarsal type, and 12 were fourth metatarsal type. Of the proximal phalangeal types, 15 were laterally duplicated supernumerary sixth digits, and 17 were medially duplicated supernumerary fifth digits. The duplicated digits of the remaining 13 originated at the distal portion of the proximal phalanx. In the middle phalangeal, proximal phalangeal head, proximal phalangeal medial, and fourth metatarsal types, the medial accessory fifth digit was an abnormally duplicated digit, which was excised. In the proximal phalangeal lateral, floating, and fifth metatarsal types, the lat eral accessory sixth digit was excised. For the children in this study, we did not perform reconstruction of the deep transverse metatarsal ligament or collateral ligament. Also, we did not use longitudinal pin fixation. Skin necrosis occurred in 10 feet that resolved, and in five of the 15 feet of the 5^th metatarsal medial deviation occurred. Conclusions: Based on the morphologic, radiographic, and operative findings, we suggest a classification method of postaxial polydactyly of the foot. We believe this is a straightforward and useful method for the treatment of postaxial polydactyly.