I would really get a 2nd opinion first, from a Specialist, before you commit to the surgery.
Next, sprains, are injuries to the muscles/tendons. Not the bone.
WHY would fusing your bones, help?
Limiting ankle movement, can then, to me, create other problems & pains.... afterward. Maybe even in a handicapping manner... physically or limit your mobility...
And I personally would, consider other manners of treatment first.
I would not want to fuse my bones together in such an important joint.
Have you ever tried physical therapy?
Had recommendations to strengthen your muscles, in that area?
Or is the problem, a problem of your joints???
Acupuncture helps pains etc.
I had it for my morning sickness/migraines as well, when I was pregnant both times. And it was the ONLY thing that got rid of it.
Friends have had it for their back pain etc. or other bodily ailments. They liked it.
Before you commit to any surgery, which would fuse your bones, I would really get a 2nd or even 3rd opinion, first.