Is Fusion Brace Better Than Ankle Replacement?

after a lot "try of this",exrays,therapy and then the offer is either ankle fusion OR ankle replacement. there is a brace called :"AFO'. before surgery as a last resort, why wasnt the fusion brace offered before surgery. i am glad i found out before scheduling the surgery. i have only been able to walk aspprox 15 minutes before the pain become severe. i sit a lot and gain weight and lose muscle tone but not fat. i am greatful for the brace but now need an exercise program to get back off of the couch.