Thumb duplication classifications: Is there still a need for improvement?

This study aims to compare the usefulness of two systems in classifying thumb duplication cases and give some examples of the cases we believe that are unclassifiable.Between January 2011 and January 2018, a total of 50 patients (29 males, 21 females; median age: 46.4±68.3 months; range, 1 to 318 months) with thumb duplications as assessed according to the Wassel and Rotterdam classification systems were included.Duplication was present in the right hand in 28, in the left hand in 21, and in both hands in one patient. According to the Wassel classification system, 45 patients could be allocated in any of the types; however, five patients could not be classified. According to the Rotterdam classification, 47 cases fell into one of the classifications; however, three cases could not be classified.Despite efforts to find the best classification system for thumb duplications, the proposed systems may not fully cover the presented radial polydactyly cases, and additions to the system are required.