Oof sorry to hear this dude! I know some members in the past have had fistula surgery, hopefully they will chime in.
Personally I had a very minor fistulotomy when I had my abscess drained, but it wasn't a real "full fledged" fistulotomy, more just opening and scraping out the area where the abscess was to disrupt any fistulous tract that was forming.
As I understand it, for fistulas like yours, they use a string to hold the incision open so that it can heal from the inside out (as opposed to outside in which would just trap more "gunk" and cause another abscess). When I had my abscess problem, I did a lot of searching on both abscesses and fistulas and posted a couple of links that I found helpful here:
http://anal-fissure.org/references-websites-facts-f5/reading-on-abscesses-and-fistulas-t2256.htmThe second link was pretty detailed and easy to understand.