I am sorry about your back.
I am not sure that you should be selling all of your heels. Once you are done with PT you are going to have to keep exercising to keep your muscles strong to support your spine. If you do this, you may be able to wear your heels at least for a few hours. You may not be able to wear them for as long, but you could get more appropriate shoes for that.
Obviously, your doctor will also make recommendations.
But don't do something that you might regret later when you haven't started PT yet.
Good Luck !