My Daughter's Terrible Back Condition

My daughter is twelve and is very active. She is now extremely restricted to what she can do now that she has been dealing with severe back spasms. Her back problems put her in extreme pain to the point that sometimes she can't even move. She has tried muscle relaxers and stretches, but neither worked. Her untreatable pain stops her from playing sports and being active, which is all she wants in the summer. What's strange is that the pain only occurs in the summer or on very hot days. I've taken her to the doctor and a physical therapist, and the stretching and medication did not help or relieve her pain. It makes me sad that she can't go out and run around and be active (or even touch her toes)like other kids. I really hope someone can help us so she can stop worrying about how much pain she is in becasue of her lower back.