On-top-plasty reconstruction for thumb triplication

Thumb triplication is a very rare pattern of radial polydactyly that presents as a more complicated form of thumb. Because of its morphological complexity, treatment often requires surgical ingenuity in addition to the conventional surgical treatment algorithms for duplication. We report the case of thumb triplication on the right hand of a 17-month-old boy. We performed on-top-plasty of the ulnar thumb over the intermediate thumb, and achieved a functional and aesthetic thumb. The technique of on-top-plasty is effective for finger reconstruction that maximizes the use of limited tissue and is widely used for treating hand trauma and congenital hand anomalies. In the present case, on-top-plasty contributed most effectively to creating a sufficiently sized thumb, achieving interphalangeal optimization by joining the extra middle phalanx with the proximal phalanx, and securing the first web space by moving the ulnar thumb laterally.