Hi @susanjane77, just Google "!2 Poses vs Osteoporosis" Dr. Lauren Fishman and you'll find his video with a discussion of his study plus other adaptations.
My doctor also suggested I get a mini trampoline (rebounder) to improve bone density in my hips. I've added rebounding to Dr. Fishman's yoga routines. I sent away to his office for a DVD of the second series of 12 poses.
If you want to take a look at rebounding, Earth and Owl has many good videos. You can also Google Earth and Owl rebounding videos to see if rebounding interests you..