Feasible and accurate occipitoatlantal transarticular fixation: an anatomic study.

BACKGROUND: Defining the anatomic zones for the placement of occiput-C1 transarticular screws is essential for patient safety. OBJECTIVE: The feasibility and accuracy of occiput-C1 transarticular screw placement were evaluated in this anatomical study of normal cadaveric specimens. MATERIAL AND METHODS: Sixteen measurements were determined for screw entry points, trajectories, and lengths for placement of transarticular screws, as applied in the technique described by Grob, on the craniovertebral junction segments (occiput-C2) of 16 fresh human cadaveric cervical spines and 41 computed tomographic reconstructions of the craniovertebral junction. Acceptable angles for screw positioning were measured on digital x-rays. RESULTS: All 32 screws were placed accurately. As determined by dissection of the specimens, none of the screws penetrated the spinal canal. Screw insertion caused no fractures, and the integrity of the hypoglossal canal was maintained in all the disarticulated specimens. CONCLUSION: Viable transarticular occiput-C1 screw placement is possible, despite variability of the anatomy of the occipital condyle.