I just searched pisiform removal in the healing well search bar above and it came up with quite a lot of info from 2003!!! Have a search and a read and see if any of the info is still relevant for you.
I attended a RA support group a few years ago and some one there was having it done, unfortunately I never found out if it was successful. She was in so much pain before the surgery.
I'm sorry I don't know any thing about it. I have wrist splints which I often wear at night and sometimes for work. MY OT has made me two sets, a resting splint and a working splint as I teach art and need fairly good movement. They can be uncomfortable but I get the splints adjusted as my wrists swell or go down, the splints may rub in different parts. I also wear a sock bandage underneath but they still get sweaty.
The OT's are very ameable to adjusting them for me.
I get a lot of swelling along tendon sheaths and suffer from carpel tunnell as a consequence, I get alot of numbness and sore wrists.
Best wishes, sorry you are having such trouble, I'd talk to a physio they are always very helpful. Golitho