Insertion of one or two electrodes into the epidural space for the treatment of certain chronic pain conditions (refractory back pain after back surgery, neuropathic pain, complex regional pain syndrome, refractory cardiac angina, amputation pain). The electrode delivers a small electrical field to a certain area of your spinal cord to modify and mask pain messages to the brain. a cable connects the electrode to a generator with a battery which is implanted under the skin. Spinal cord stimulators can be placed in the epidural space of the lower back, chest and neck. It can be performed in just one procedure or with a trial in two procedures 1 to 2 weeks apart.