they are not necessarily permanent
basically what happens is the de-curve the spine into a more (not perfect) straight form then add the steel for support, after that they "sprinkle" bone fragments into the spine which will strengthen it in place
after a year the spine is fully fused the hardware does not become necessary but it stays in unless you get an infection then they would go back in and remove it
i had an s curve and they only fused the top one so i have full rotation on the bottom
and like i said i have family friends who had it before it was as advanced and they can still do back bends and stuff with just a solid less flexible rod
so with a lot of stretching and physical therapy i will be fine
maybe better cause i was terribly un-flexible in the first place