  This paper has two objectives: we first generalize the theory of
Abhyankar-Moh to quasi-ordinary polynomials, then we use the notion of
approximate roots and that of generalized Newton polygons in order to prove the
embedding conjecture for this class of polynomials. This conjecture -made by
S.S. Abhyankar and A. Sathaye- says that if a hypersurface of the affine space
is isomorphic to a coordinate, then it is equivalent to it.
