From what I understand the bamboo will grow towards the light. If you can make the light source come from a single direction and turn it periodically it might start to circle.

Found this during a search. I totally thought this was formed while the cane was young and pliable around something.
Heh.
Guess you learn something new every day =)

Refer to the first column on page 2 where they speak specifically about dracaena.

Here is a link that might be useful: heliotropism

The word Dracaena doesn't appear in that article, but you might enjoy this discussion about other Dracs, Hookilau: http://forums2.gardenweb.com/discussions/2856506/can-this-dracaena-be-saved?n=10