If you open up the back of someone who had a lumbar epidural steroid inj 1 yr ago would you see white powder in the epidural space?

No: The white powder you see in the vial before they reconstitute it is the dehydrated, concentrated form of the drug. After it is injected, it is metabolized within a few weeks. There would be no trace of it left.

Epidural medication: The medication will be absorbed into the vascular system. It is then metabolized. No white powder should be seen.

Epidural steroids: On few occasions the white material can be seen which has become stuck to the yellow ligament covering the nerves.

Usually No: However if surgery is done shortly after an epidural injection and a particulate steroid was used then I have heard from surgeons who have said they see the white powder.