A Classification System of Radial Polydactyly: Inclusion of Triphalangeal Thumb and Triplication

Purpose: Radial polydactyly is a congenital anomaly with a wide range of manifestations. Current classifications do not have the capacity to classify all different types of radial polydactyly when combined with triphalangeal components. The objective of this study was to test an adjusted classification and nomenclature that allows classification of triphalangeal components and triplication in radial polydactyly. Methods: Patients from 1993 to 2006 with radial polydactyly (N = 104), a total of 121 affected hands, were identified from the hospital database. All x-rays were carefully examined and classified according to the existing classifications for radial polydactyly and a modified classification. In the modified nomenclature, Wassel's level of duplication is preserved. Type VII and VIII are assigned for partial or complete duplication of the carpal bones according to Buck-Gramcko. Triplication and triphalangeal components can be assigned to each type of radial polydactyly by suffixes. Symphalangism, deviation, and hypoplasia can also be classified. Triplication on different levels of the thumb is classified by determining and including the different types of the original Wassel classification. Results: Eighteen thumbs could not be classified according to existing classifications for radial polydactyly with triphalangeal components or triplication. Using the proposed classification, all patients could be classified. Conclusions: We propose a modified classification that is a practical and utilitarian scheme for nomenclature of radial polydactyly and that may assist comparison of treatment outcomes and individual cases. Type of study/level of evidence: Diagnostic II.

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