Do you want to know more about Nerve Root Block and Epidural Block Radioablasion of Facet Joints? A nerve root block is an injection of local anesthetic (numbing medicine) and steroid injected under X-ray guidance into the area where the nerve exits the spinal column. A nerve root block is usually ordered by your doctor for pain in the arm or leg that follows the path of a single nerve.||| A lumbar RFA is a procedure that uses radio waves to stop the lumbar medial branch nerve from transmitting pain signals from the injured facet joint to the brain. The procedure calls for a needle to be inserted through the skin and guided with X-ray to the correct site overlying the medial branch nerve.