A clinical morphologic study of the C2 pedicle and isthmus.
OBJECTIVE
This anatomic, radiographic study investigated locational differences in the C2 pedicle and isthmus [pediculoisthmic component (PIC)] and characterized its narrowest section for clinical application in posterior C2 screw fixation.


METHODS
Structures surrounding the transverse foramina of 30 dry C2s and 10 C3s were compared morphologically. Spinal CT scans of 32 Chinese adults were subjected to volume rendering and multiplanar reconstruction to identify the narrowest C2 PIC, and correlative parameters were measured and analyzed.


RESULTS
Inferior C2 and C3 structures were morphologically similar. In superior view, the C2 superior facets lay on the transverse foramen and the upper portion between superior and inferior facets was flat (average mediolateral angle, 11.1° ± 2.4°). In inferior view, the posteroinferomedial portion of the C2 transverse foramen displayed a partially tubular structure (average mediolateral angle of projection, 42.6° ± 4.9°). Average height and width were 11.6 and 6.9 mm. The inner medullary cavity was elliptical and the middle site of endosteal diameter was 3.3 ± 1.9 mm. Medial internal cortical bone was significantly thicker than lateral bone (P < 0.01).


CONCLUSIONS
The PIC is located between superior and inferior C2 facets. The superior flat area is the isthmus and the inferomedial area connecting the inferior facet and vertebral body is the pedicle. The pedicle is partially tubular and projects posteromedially to the transverse foramen. The narrowest PIC section is the narrowest point of the C2 pedicle. Considering its thin lateral cortical bone, medial and superior pedicle screw placement and preoperative CT reconstruction are recommended.
Department of Orthopedics, Affiliated Hospital of Xuzhou Medical College, Xuzhou City 221000, China. cnyuanfeng@hotmail.com
Feng
F
Yuan
Hui-Lin
HL
Yang
Kai-Jin
KJ
Guo
Jiang-Shan
JS
Li
Kai
K
Xu
Zhi-Ming
ZM
Zhang
Tian-Si
TS
Tang
D000293:Adolescent; D000328:Adult; D000368:Aged; D002574:Cervical Vertebrae / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D055815:Young Adult