Hmmmm... I also have fantasies of bone breakages. But I never looked at why. In the fantasies, it is always me lying there, sprawled out at some horrible angle, a person finding me and screaming for help... and that's it. Sometimes it gets to the hospital... but from there on the fantasy gets boring. Maybe it is just something to preoccupy my mind...
I was in half a cast as a kid for a week- had so many growth lines, they couldn't tell if it was fractured or not. So they splinted it toes to knee and wrapped it thickly. It does get boring very fast.
It is also a lot harder to break your own bone than you'd think. The body tries to preemt injury at all costs. I'd say just ask for attention in here or with friends =) Throw a party or bbq.