I was doing some reading here this morning and began to wonder whay it takes a spine so long to fuse while a broken arm, or leg seems to heal up or show signs of fusion much, much quicker. To me when a cage is put between the vertebrae and locked down with the rods and screws there shouldn't be any more of a gap then in a broken bone. Many, many years ago I broke my ankle and had 2 plates and 46 screws put in and that showed signs of healing, or fusing, pretty quickly. Just curious. Any thoughts?