I've got the upper back pain too ;-(
It actually started getting worse about 1 1/2 yrs post fusion but I have a sagittal imbalance which causes me to crane my neck forward and up and causes strain on those muscles. I get relief with heat wraps, and Percocet once/day. It definitely is worse on my more active days and feels like yours, muscles ripping and burning. Located in the scapular region. The Thermocare heat patches are nice too but can be expensive to use every day.
May 2008 Fusion T4 - S1, Pre-op Curves T45, L70 (age 48). Unsuccessful surgery.
March 18, 2010 (age 50). Revision with L3 Osteotomy, Replacement of hardware T11 - S1 , addition of bilateral pelvic fixation. Correction of sagittal imbalance and kyphosis.
January 24, 2012 (age 52) Revision to repair pseudoarthrosis and 2 broken rods at L3/L4.