Create polyline from spline

Set Splinetype to 5 instead of 6.

 

Use PE command, then S command to fit spline to polyline.

 

Explode newly created spline.

 

Use polyline edit  PE” command again before anything else, select M for multiple, then P for previous (will select objects from previous command), then do the Join subcommand within PEdit.

 

You now have a polyline created from a spline.