The location of the pedicle and pars interarticularis in the axis.
METHODS
This is an anatomic and radiologic study on the lateral mass of the C2 vertebra.


OBJECTIVE
To define the location of the pedicle and pars interarticularis in the C2 vertebra.


BACKGROUND
Transpedicular screw fixation of the C2 has been addressed in the literature. However, the use of the anatomic terminology of the pedicle or pars interarticularis (isthmus) in C2 is confusing in most of orthopaedic and neurosurgical literature since C2 is considered a transitional vertebra.


METHODS
Twenty dry C2 vertebrae were obtained for observation of the external anatomy of the C2 from superior, lateral, and inferior views. Six C2 vertebrae were harvested from cadavers and sectioned in the sagittal, horizontal, and coronal planes to observe the internal structures of the lateral mass using high resolution radiographs.


RESULTS
Based on observation, the pedicle of the C2 vertebra is defined as the portion beneath the superior facet and anteromedial to the transverse foramen. The pars interarticularis or isthmus is defined as the narrower portion between the superior and inferior facets. No remarkable difference in bone density and trabecular bone orientation between the pedicle and pars interarticularis was noted.


CONCLUSIONS
It is still more appropriate to call this procedure "transpedicular screw fixation" in the C2 to avoid confusion, although this technique requires placing a screw from the posterior aspect of the inferior articular process through the isthmus and pedicle into the vertebral body.
Medical College of Ohio, Toledo, Ohio 43614, USA.
N A
NA
Ebraheim
J
J
Fow
R
R
Xu
R A
RA
Yeasting
D000368:Aged; D001368:Axis, Cervical Vertebra / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D001863:Bone Screws / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D021801:Zygapophyseal Joint / Q000033:anatomy & histology* / Q000601:surgery