HI Guys

I'm a 49 year old male with a five year history of sciatic pain. The pain corresponds with the S1 nerve path apart from a small area in the front of my left thigh.
Due to my symptoms it was thought there was a problem with L5-S1 disc but after all conservative methods failed and a discectomy proved unsuccessful, I had an L5-S1 fusion via the Axialif method last October.
Still no joy, the nerve pain remained the same, however from the moment I woke from surgery I was aware of a lot of ligamnet pain from the Sacro-illiac joint, having already done some research on SI joint syndrome I decided to have a course of Prolotherapy which has completely stopped the joint pain but as of yet the nerve pain has not improved.
My question are these;

1)Has anyone had a similar experience with SI joint syndrome and had success with prolotherapy or some other method?
2)Has anyone had experience with this type of nerve pain and found a different reason for it. (Apart from nerve root tension, herniated disc etc)
3) Has anyone out there ever had their SI Joint fused, and if so what was the success?

Hope you guys can help.

Regards

Rob