Go to all mediums or better yet, all shallows. I'm using mediums now, wishing I had gone to all shallows.
Good luck with your back. IMO; resist all temptation to have surgery. Keep yourself moving 'even when it hurts' (walking every day helps me tremendously) Find a 'pain clinic' with a good psychologist, one trained in pain relief (the mind is an amazing thing). Ask your therapist for ultra sound treatments, especially when having 'acute' pain, its wonderful. "TRY" to stay away from narcotics, regardless of recommendations (this one coming from a former addict), using them 'as needed' only.