That last post was better - if the star nut is broken, then it must be replaced. If it is not broken then the stem needs to be tightened if the handlebars/fork jiggle forward/backward inside the head tube.
If the handlebars are actually TWISTING from side to side then the two bolts on the back of the stem need to be tightened only. If the handlebars slip forward/backward inside the stem, then the bolts on top of the stem need to be tightened.
I went on a rant because you said "with the front wheel lodged between your legs, (ultimately trapping the wheel), can you turn the handlebars" and related that to the star nut. That has nothing to do with the star nut.
The most likely thing is:
a: The two bolts on the back of the stem are simply loose and need to be tightened because the bars actually twist side to side. OR...
b: The headset is loose and needs to be tightened as listed in my first post.
If the headset is loose, but can't be tightened as listed in my first post, then I went on to explain the star nut and the removal/installation procedures. No rant on that though, just an explanation.