Last year I had some issues with my upper back (between shoulder blades) that could cause my shoulders to numb. A few chiropractor sessions and exercises to move my shoulders back and down (imagine getting your shoulder blades to touch) solved the problem. I also had a tender spot in my lower back for a few months (due to a couple of nights on a sleeper sofa), and this problem was solved by hanging upside-down for a few minutes nightly using a inverter table.