Lateral Polydactyly of the Foot: Surgical Outcomes Based on a New Classification.

Background: The objective of this study was to propose a novel classification for lateral polydactyly of the foot that integrates both visual appearance and radiographic findings and to delineate surgical techniques and their outcomes based on this classification.

Methods: This study enrolled 148 feet from 126 patients who underwent initial surgery at our hospital between January 2009 and July 2021. The new classification system was derived from visual appearance according to the Hirase classification and radiological bifurcation level (D: distal or middle phalanx, P: proximal phalanx, and M: metatarsal). Incidence rates, surgical procedures, and surgical outcomes were compared across each type.

Results: Morphologically, 25 cases were classified as type A, 43 cases as type B1, and 80 cases as type B2. The branching level was categorized as D in 81 feet, P in 41 feet, and M in 26 feet, with 68 feet (46%) classified as B2-D type. Excision of the sixth toes was performed in all type A cases, whereas the majority of type B cases required excision of the fifth toes. Revision procedures were conducted on 8 feet. Three patients with type A-P classification developed painful hammer toe deformities as a late sequela that necessitated extensor tenolysis and metatarsophalangeal joint contracture release during their school-age years.

Conclusions: The classification system based on the combination of visual appearance and radiological branching level was both straightforward and beneficial for surgical planning and for predicting surgical outcomes and late sequelae.