Quick note from a multiple back fusion kind of guy. The Back braces work. They will provide you with support to keep you from torquing things that shouldn't be torqued. That being said, I never wear the brace unless I am at great risk of compressive shock to the spine which I would have nt control over, (ie. a pothole at speed...) I never wear it otherwise due to the fact that it will let you allow the muscles to become dependant on the support, at the expense of atrophy of muscle groups that you need to work REAL HARD to strengthen.
I can't help you with what will work best for you. I'm a S-3 through L-3 kinda guy, and that lets me wear a brace like a corset that squeezes and stretches me like a corset. (goes on kind of the same way... shut up you guys...) I don't know if you can get one for where your beat up. Go to a prosthetics shop and tell them what your situation is and what you want out of the brace, (safety for the unexpected), and they should be able to help you out...
The previous commentary about the right questions to ask the doctor is right on the mark too in my opinion. My doc told me that it would be suidice to ever ride again, and it turns out that he would have said the same thing if I had had him operate on my foot.....
Cheers, be carefull, and remember how to get old... Look forward to the next day, and wake up for it!