Titles get vacated for injuries lasting longer than 30 days I think. I don't know why they'd do it in Asuka's reign. I understand that's the "rule", but they don't even follow it all the time. Long live the Empress.
Oh, nevermind. She's probably going to get called up and nobody can beat her without being eaten alive by the crowd.
Well the rule is that you need to be able to defend your title every 30 days at a minimum. Sucks for Asuka though, she's amazing. She'll get it back.