Posterior occipitocervical (C0-3) fusion using polyaxial occipital condyle to cervical spine screw and rod fixation: a radiographic and cadaveric analysis.

Numerous conditions affect the occipitocervical junction requiring treatment with occipitocervical fixation. In this paper the authors present their technique of craniocervical fixation achieved with the cephalad extension of posterior C1-3 polyaxial screw and rods to polyaxial screws placed in the occipital condyles. They retrospectively analyzed occipital condyle morphology obtained from CT analyses of 40 patients with normal cervical spines, evaluated occipital condyle screw placement feasibility in 4 cadavers, and provided a case report of a 70-year-old woman with rheumatoid arthritis, basilar invagination, and atlantoaxial instability who was treated with this novel technique. Based on radiographic analysis of occipital condyle anatomy, they concluded that on average a 3.5-mm-diameter x 20- to 30-mm-long screw can be safely placed at an angle of 20-33 degrees from the sagittal plane. Overall, measuring the condylar heights (mean [+/- SD] 10.8 +/- 1.5 mm, range 8.1-15.0 mm), widths (mean 11.1 +/- 1.4 mm, range 8.5-14.2 mm), lengths (20.3 +/- 2.1 mm, range 15.4-24.6 mm), and angles (mean 32.8 +/- 5.2 degrees , range 20.2-45.8 degrees) by using CT studies is an accurate and precise method. This finding correlates with the results of prior anatomical studies of occipital condyles and is important in the planning of craniovertebral junction surgery.