I work at an interventional pain management clinic, and we see some success with TENS units in conjunction with other therapies. For the herniated disc and DDD, I often see my doctors prescribing and performing discectomies - with a lot of success. You may want to look into a discectomy if the ESI doesn't give you the relief you're looking for. Interventional pain management is an interesting specialty - we see people every day in chronic pain, and I love when we can help a patient get relief.