  The significance of zero modes in the path-integral quantization of some
solitonic models is investigated. In particular a Skyrme-like theory with
topological vortices in (1+2) dimensions is studied, and with a BRST invariant
gauge fixing a well defined transition amplitude is obtained in the one loop
approximation. We also present an alternative method which does not necessitate
evoking the time-dependence in the functional integral, but is equivalent to
the original one in dealing with the quantization in the background of the
static classical solution of the non-linear field equations. The considerations
given here are particularly useful in - but also limited to - the one-loop
approximation.
