MORPHOLOGIC CHARACTERISTICS OF HUMAN CERVICAL PEDICLES

Study Design. Cervical pedicle morphology was investigated using manua l and computed tomography measurements. Objectives. Normal anatomic va riations of the cervical pedicles were measured to evaluate their safe ty as anchors for posterior cervical fixation systems. Summary of Back ground Data. There have been no cervical pedicle measurements on a lar ge number of specimens. No study has ever measured the inner pedicle d iameter. Methods. Fifty-three spinal columns (C2-C7) of Euro-American origin identified by age, sex, and height (318 vertebrae or 636 pedicl es) were measured using a digital caliper, a goniometer, and computed tomography scanning. Results. The pedicle axis lengths were similar fr om C3 to C7 (except far shorter C2 pedicles). In the horizontal plane, the medial inclination of the pedicles followed the cervical spinal c ord enlargement. In the sagittal Ina plane, the pedicles were directed superiorly in the upper spine and inferiorly in the lower cervical sp ine. Some pedicles had no medullary canal (i.e., were solid cortical b one: 0.9% C2 2.8% C3 and C4, and 3.8% C5 ii pedicles). The outer pedic le width was smaller than the height in most of the pedicles. The inne r pedicle width was equal to or smaller than 2 mm in 13.2% C2, 72.6% C 3, 67.0% C4, 62.3% C5, 51.9% C6, and 16.0% C7. The outer pedicle width was equal to or smaller than 4 mm in 8.5% C2, 75.5% C3, 35.8% C4, 13. 2% C5 and C6, and 6.6% C7 pedicles. The thinnest pedicle cortex was al ways the lateral cortex, which protects the vertebral artery. Measurem ents of the posterior pedicle projection also were taken. Conclusions. These data provide anatomic limitations to pedicle screw use in the c ervical spine.