Zeus: I am so sorry that has happened. I also have four very bent fingers, and wow are they ever painful some days.
Your question is about how to stop more from happening. I am afraid that to the best of my knowledge you cannot. Unless you can get the disease activity under control. The path is fairly clear, see your rheumatologist regularly, Do what is suggested, do the labs, and be the squeaky wheel.
The way I have found is medicine. It will not stop overnight. But know this, every bit that you lose in joint flexibility never comes back. It is best to not waste even a day.