In most cases, the fusion is augmented by a process called fixation, meaning the placement of metallic screws (pedicle screws often made from titanium), rods or plates, or cages to stabilize the vertebra to facilitate bone fusion. The fusion process typically takes 6-12 months after surgery. During this time external bracing (orthotics) may be required. External factors such as smoking, osteoporosis, certain medications, and heavy activity can prolong or even prevent the fusion process. If fusion does not occur, patients may require re-operation.