Fixing a computer bench...? The pneumatic pole on my chair stool has... pushed through the 5-legged...

The pneumatic pole on my chair stool has... pushed through the 5-legged end so that when I sit in it, I'm simply balancing on this pole. It's really unstable and I've fall backwards twice in it. The pole also dragged across the mat so I have to PICK UP the stool to move it.

Here's a picture: http://i40.photobucket.com/albums/e242/Q...