Chris with plastered arm

[Chris_Lover]

It's something I've been thinking of for awhile, maybe some of you could help me find an answer. I saw some pics where Chris has her left arm plastered and I was wondering what happened to her. Had she an accident or a fall that resulted in a broken bone or a torn ligament?
These pics must be from 1978/1979, soon after "Sisters of the moon" was released (since on the japanese cover of this single she has the plastered arm).
I hope I used the correct medical term; if not, please feel free to correct me.
As always, thanks for your help