If you have AutoCAD....and are willing to pay a little... www.4d-technologies.com/polyline_specialist
Very powerful tool. Runs as an AutoLISP 3rd party add-on routine inside AutoCAD full version, (which btw won'trun in AutoCADLT because there is no 3rd party support in LT). You will probably need to do some exporting/ importing around,but this software should work for youif you are patient with it. If you'd like you may post a file (.dxf or .dwg) witha spline and I'll send you back arcs. I am up for the challenge!
I don't think this is what you want, but if you create a drawing
of the sketch you can export it as a .dxf and tell it to export splines
as polylines. If you then import it into Pro/E it comes in as a load of