Why? I'm not quite sure I understand -- are you planning to break your own ankle? My honest answer is that this is a really bad idea. Ankle breaks are no fun, and depending on the injury, can be very complicated to repair and take a long time to heal. If it's attention you want, I suggest you (at 18?) speak with a trusted adult about your feelings -- and very possibly a therapist as well.
MISERY. Watch the movie "misery" and you'll find a way.