I am sorry to read such a sad message! Please tell us a little bit more about situation if you can. E.g, was the device positioned correctly during surgery? Immediately thereafter? Did you get a DEXA scan before surgery? Did the device subside? Did you obtain your imaging studies and radiologist reports?
Sorry for the questions, but we are here to help. And yes, unfortunately, device subsidence can be a problem and is usually due to localized osteoporosis and/or incorrect device placement. When the two conditions exist, the problem is almost inevitable!
I hope we can help you with your next steps. In the meantime, you may find these links helpful:
http://www.adrsupport.org/images/uploads/Regan.pdf
http://www.adrsupport.org/forums/f55/depuy-spine-9504/