The Wassel classification is used to categorise radial polydactyly, based upon the most proximal level of skeletal duplication.[1]
| Type | Level of duplication | |
|---|---|---|
| I | Distal phalanx | |
| II | Interphalangeal joint | |
| III | Proximal phalanx | |
| IV | Metacarpophalangeal joint | |
| V | Metacarpal | |
| VI | Carpometacarpal joint | |
| VII | Triphalangia |