pedicle screws are screws which are placed in the pedicles of the spine, usually in the lumbar area, and help to hold the spine together and immobile, while the bone placed along the side of the spine, or in between the vertebral bodies, is fusing.  Seen here are four pedicle screws, placed in the pedicles of L4 and L5 on each side of the spine, and the screws are held together with rods.  Generally, these devices are made of a titanium alloy, and are compatible with MRI scanning.