The C2 "Parsicle" Screw: Introduction of a Novel Posterior Surgical Technique For Upper Cervical Fixation.

The instrumentation of C2 is technically challenging given the anatomic complexity of the upper cervical spine. Although the placement of C2 pedicle screws may be safer than transarticular screw placement, the inconsistent location of the transverse foramen and vertebral artery precludes placement of such screws in up to 26% of patients. In cases where vertebral artery anatomy prevents the safe placement of a pedicle screw, a pars screw is an excellent alternative. However, pars screws must stop short of the vertebral foramen, limiting the typical length of these screws to only 14-18 mm. The associated purchase and rigidity are compromised compared with the pedicle screw. A modified C2 fixation technique was developed by our group which we have named the C2 "parsicle" screw reflecting the hybrid nature of the screw incorporating aspects of pars and pedicle screw fixation.