So what exactly are they gonna do?  Are you having any hardware put in?  
I had two rods running about the full length of my back with multiple plates & screws to hold a bone graphed that was shaved off my left hip, they only had to stay in atleast a year, they could have stayed in forever but I'm a thin guy and the screws at the top started to poke through and would feel uncomfortable when I laid on my back, so I had it all removed.  I ended up with a scar running the full length of my back, had about 60 staples in it.  Still have some metal left in me, have a rod and pins in my right hip.