Posterior cervical screw systems are intended for use in fusion procedures of the cervical spine and/or craniocervical junction and/or cervicothoracic junction for: 1) spinal fractures and dislocations; 2) deformities; 3) instabilities; 4) failed previous fusions; 5) tumors; 6) inflammatory disorders; 7) spinal degeneration, 8) facet degeneration with instability; and 9) reconstruction following decompression to treat radiculopathy and/or myelopathy. These systems are also intended to stabilize the spine in the absence of fusion for a limited time period in patients with tumors involving the cervical spine in whom life expectancy is of insufficient duration to permit achievement of fusion.