Case ReportOn-top and side-to-side plasties for thumb polydactyly

•“On-top” and “side-to-side” plasties are techniques used for treating thumb duplications.•The functional results of these techniques have not been reported in the literature.•We report on two cases and document excellent functional results.

Introduction“On-top” and “side-to-side” plasties are techniques used for treating thumb duplications in which one thumb is adequate proximally and the other thumb contains a better pulp and nail distally. The detailed functional results of these techniques have not been reported in the literature. We report on two cases.Presentation of casesThe first case had Wassel type VI duplication. The ulnar duplicate had a functioning interphalangeal joint and the radial duplicate had a functioning carpometacarpal joint. “On-top” plasty was done by putting the distal part of the ulnar duplicate on top of the proximal part of the radial duplicate. At 10 years after surgery, the outcome was excellent both cosmetically and functionally. In the second case (Wassel type VII with a zigzag deformity), the radial duplicate had a hypoplastic distal phalanx with no nail. The ulnar duplicate had a functioning interphalangeal joint and the radial duplicate had a functioning carpometacarpal joint. “Side-to-side” plasty was done by joining both thumbs side-to-side at the level of the proximal phalanx. At 3 years after surgery, the outcome we considered acceptable cosmetically and excellent functionally.DiscussionWe could not find similar cases in the literature with detailed long-term postoperative results.Conclusion“On-top” and “side-to-side” plasties in the management of specific cases of thumb polydactyly obtain excellent functional results with excellent or acceptable cosmetic outcome.