[Verification of thumb-specific muscles in a triphalangeal thumb with magnetic resonance imaging].

The presence of three phalanges in the first digit is considered to be a relatively rare congenital hand malformation. Six groups of this deformity can be distinguished: some digits are opposable, others resemble a non-opposable five-fingered hand. In cases of a hypoplastic thenar region with a restrained opposition, a clear verification of thumb-specific musculature has been hardly possible. We report of the possibility of a non-invasive identification of thumb-specific muscles by means of magnetic resonance imaging.