This procedure is recommended when a set of vertebrae becomes loose or unstable. The surgeon joins two or more bones (vertebrae) together through the use of metal rods, screws, and bone grafts. The bone grafts complete their fusion in 4–8 months following the surgery, securing the spine in the correct position. The procedure is also used to treat spinal instability, fractures in the lumbar spine and, severe degenerative disc disease.
The fusion process is followed by fixation that involves fitting of metallic screws, rods, plates or cages to stabilize the vertebrae and accelerate bone fusion. After surgery, 6-12 months is the ideal time for complete fusion to take place.
The screws(called pedicle screws) are passed through the pedicles of the vertebra and they enter into the body of the vertebra and grip them.