How is it possible?

My dad went into the rabbitry this morning for a routine check up on how the rabbits were doing. he discovered that the 2nd place junior doe at convention had broken her back. she had started chewing her toes and my dad realized there was no hope. how does a rabbit break there back in there cage? she was a gorgeous doe and she will be greatly missed. I am wondering if there is anything i could do to prevent this from happening again.