InHisHands, there are a couple of reasons where having a bone scan can make a difference!
If the scan shows osteoporosis then there is a treatment called Pamidronate Infusions which can lessen the pain of CRPS by helping to move calcium from the blood stream into the bone.
It is thought that osteoporosis is the cause of some of the deep bone pain of CRPS.
Another reason a bone scan can be useful is that it can sometimes help to make a diagnosis of CRPS and if your treatment is dependent on an Insurance company needing "proof" of the disease, then a scan that shows irregular osteoporosis which is confined to your areas of severe pain then this is often all they will need to give the OK for treatment.
My first scans several years ago at the beginning of the disease were normal, now, 7 years later I have severe osteoporosis in my CRPS affected areas.