I too have a partial achilles tear and also degenerated tissue. I'm going to have a reconstruction done on March 17th where they may have to take additional tendon out of my big toe to rebuild it. I've been dealing with this since last Jul/Aug, getting injections and such. I finally got someone to do a MRI and it showed the tear.
I'm concerned about the cast because I have "hot feet". I just read a post about cast caustrophobia and I may have that as well. We will see how it goes, please keep me informed on your progress.