[Distinctive features of the os naviculare pseudarthrosis vs the os naviculare accessorius].

We report on two cases in which the differential diagnosis between an os tibiale externum (os naviculare accessorius) and a post-traumatic pseudarthrosis of the os naviculare was subject to discussion.Both patients had suffered an acute trauma in the region of the middle foot and showed identical clinical symptoms. Conventional X-ray did not allow a definite classification of the diagnosis either.However, this was possible in both cases by virtue of typical signs evidenced by computed tomography and magnetic resonance imaging.