Lumbar fractures and Osteoporosis

I don't remember being told that osteoporosis might be a post-op complication of an RNY - GB. I'm 56 y/o and 285# . Goal weight is still 175#. I'm almost 3 years out now and I had lost 125lbs at a year. Then at 15mos post-op, I felt a pop in my back while I was getting stuff up from the basement.  An MRI found new and old compression fractures of my lumbar spine.  My bone density test was high normal. I'd already been taking Calcium and Vit. D and good multi-vitamins. Last October I fell and broke my knee and sacrum.  I was having so much more pain in my back that I had a second MRI and they found yet another compression fracture.  Since I've been sitting around doing next to nothing for the past 4 months I've gained 20lbs.  I have been officially in menopause for 2 years and I'm taking natural forms of estrogen and progesterone, prescribed by my docotor. Does anyone else know anything about these problems? Are they a known complication of GBS that I just pushed into the background of my mind?

Inability to absorb calcium is a know side effect of RNY. It follows that anything that can happen due to lack of calcium is a direct result of RNY.