I bought a Power Plate in 2008 and really loved it for quite a long time, though eventually stopped using it because I have glaucoma, later had a huge post-surgical eye wall collapse, and had two knee replacements. Most of my doctors were worried about the vibrations. I'd had one borderline DEXA at that point but I didn't pay it much attention, since I had almost no risk factors and my other doctors told me DEXAs were not very reliable back then.
Much later I got very interested in the very gentle vibration plate developed by Dr. CT Rubin and others after very extensive research with osteoporosis in mind. My endocrinologist was involved in assessing that product and told me when I asked about it after falling and breaking my femur and getting an actual osteoporosis diagnosis, that unfortunately it had not turned out to be useful.
In Keith McCormick's book, GREAT BONES, he talks about vibrating plates on pages 572 and 573. He is cautionary that they can be harmful to the eyes, ears, joints, and even the brain and gives some exact specifications you should be sure your platform has available if you plan to use it that way.
You should be barely able to feel the vibrations. If you have spinal fractures that keep you from standard weight-bearing exercise, he says it may be worth pursuing but you clearly need to be very careful.