A friend of mine at U Maryland, Dr. Josh Abzug, was involved with an interesting study that was published last year. He and his colleagues looked at all of the reasons that patients returned to their doctors because they needed their casts changed earlier than was planned.
Casts need to be changed regularly. This is part of the package in dealing with this effective, but cumbersome, treatment option. All sorts of life mishaps can thwart our efforts to use casts.