A thoracic epidural steroid injection is an injection to temporarily ease pain in the thoracic region (the upper middle part of your back). The medication, typically a steroid, is injected to the epidural space, the area surrounding your spinal cord. The brain is able to communicate with the rest of the body through the spinal cord. If the nerves leaving the spinal cord become pinched, you may feel pain in the back and into the rib cage. The thoracic epidural steroid injection can ease the inflammation and pain, in this region.