ESI. An epidural steroid injection is a minimally invasive procedure that delivers steroids via a needle directly into the epidural space to help reduce inflammation. It is indicated for patient with radicular pain, but can be effective for other conditions as well.
Look here. Here is a nice website from beth israel hospital in boston: http://www. Bidmc. Org/centersanddepartments/departments/spinecenter/hottopics/transforaminalesi. Aspx.
Primary for leg pain. They are used primary used when there is a pinched nerve in the back that is causing leg pain, ie sciatica.
Sciatica Pain. Typically epidural injections help the most in patients that have sciatica pain due to herniated disk or spinal stenosis.