I too have been suffering from muscle spasms around and under my shoulder blades for ~16 years. I've tried all sorts of therapy that all "feel good" at the time, but ultimately never lead to permanent pain relief.
After reading a book on self treatment of trigger points (muscle spasms), I learned that there are many latent trigger points that refer pain elsewhere. In my case I found some nasty little buggers in the scalene muscles found in my neck. (I had no clue there was such pain to be found there!) I decided to try physical therapy once again, but this time focus more on the neck muscles. I found a therapist who specializes in trigger point therapy, and BINGO! I can't believe it! She knows how to get right to the source. When she digs into my scalenes I can feel the pain travel all the way down my spine and my arms.
I have to say that I had resigned to a lifetime of this pain, but no longer!
I highly recommend the following book:
The Trigger Point Therapy Workbook: Your Self-Treatment Guide for Pain Relief, Second Edition
ISBN: 1572243759
http://www.amazon.com/exec/obidos/tg/detail/-/1572243759/qid=1120071200/sr=1-2/ref=sr_1_2/002-7761526-3638409?v=glance&s=books