I've heard of it, and had my PM&R talked about it, but from what I was told it only works in the beginning. My PM&R told me a year out that he would not do the injections because they are not a good idea that far into RSD (it had also spread at this point)because they will probably not work, and might actually hurt me.
It might be a different story with each person since everyones pain and spread(if any) is different, but all the doctors I've talked to about it say that it only works within a certian time frame. I know it is also less likely to help after the RSD has spread for some reason. (Hopefully, if you havent had it already, you wont attain a spread, and will have more treatment options available). So, thats my experience with it, hope it helps.