According to a source close to the group, Matsui injured the middle finger and ring finger of her right hand, but it's unknown if those fingers are fractured. 

At the beginning of the live, Matsui appeared on the stage, and explained to the fans, "I was really looking forward to this, and participated in the rehearsal happily with vigor, but I got injured during the rehearsal, so I can't come on the stage after this." She then apologized to them in a tearful voice for not being able to participate on the live.

This live was a special event for mobile card game "SKE48 Passion For You", and approximately 800 audience who were chosen attended the live.

Source & Image: Oricon