Yeah, you'll always have arthritis in that tibiotalar joint. BUT--and this is really, really important--keep that damn joint moving at all costs. You've got to push it. I don't care if you have to use narcotics or even intraarticular steroids. The best way to fuse that joint is letting it be. The best bet on riding again (and you will), is to work the piss out of it. It'll take another year or so, I'd bet.
Can you put your last films up? I want to take a look at the tibiotalar joint.
I remember that you had external fixators, but did you have a delayed open reduction, internal fixation procedure done? Outcome may be better.
How'd you do it again? I would bet you cased a jump, like I did, but had your foot more forward on the peg so that calcaneous to talar to tibial plafond force was more efficient.
What gear? How fast? What kind of jump, if a jump?