  We examine nonlinear sigma models, in particular the Skyrme model with a
twist (the twisted Skyrmion string), which comprises a vortex solution with an
added dependence on a twist term $mkz$, where $z$ is the vertical coordinate.
The topological and Hopf charges of a twisted Skyrmion string are calculated
and are shown to be equivalent to the winding number $n$ of the vortex and
proportional to $nmk$, respectively. The principle of conservation of the Hopf
charge, which is a standard property of the baby Skyrmion model, is generalised
to cover the non-compact twisting solutions studied here.
