Vertebral Bone Quality and Prediction of Screw Loosening in Spine Fusion

Finding a way to use Vertebral CT scan will help to predict screw loosing risk in spinal fusion for degenerative spine disease. Patients who will undergo at least two spine fusion levels for degenerative spine disease will be enrolled in. Before surgery, patients will undergo a spinal QCT scan with a calibrated phantom. The calibrated bone density, at bone-implant interface, will be assessed using dual energy CT scan immediately after surgery, and six months later. The primary outcomes will be the difference between the two values of the bone implant interface. The difference between density values will be correlated to the pre-op bone density value.