[Anatomic evaluation the entry point of C2 pedicle screw].
OBJECTIVE
To study the relevant position of C(2) pedicle to C(2) inferior articular process, set up a technique of C(2) pedicle screw placement with the inferior articular process of axis as an anatomic landmark.


METHODS
Fifty C(2) bone specimens were used to measure the distance from the sagittal midline to the medial border, the midpoint and the lateral border of C(2) inferior articular process or C(2) pedicle; the width and the height of the C(2) pedicle were also evaluated. The anatomic relation between the measurements data of C(2) pedicle and that of C(2) inferior articular process were analyzed, and the technique of C(2) pedicle screw fixation was established.


RESULTS
The medial border of C(2) inferior articular process was averaged (3.67 +/- 0.41) mm lateral to that of C(2) pedicle, and the midpoint C(2) inferior articular process was averaged (1.15 +/- 0.44) mm lateral to the lateral border of C(2) pedicle, respectively. Using the C(2) inferior articular process as landmark, two techniques was established for C(2) pedicle screw placement. The entry point of method A was located in 2 mm medial and superior to the central point of C(2) inferior articular process; the entry point of method B was at the crossing point of the medial border C(2) inferior articular process with the superior quarter of C(2) inferior articular process.


CONCLUSIONS
There is a steady anatomic relation between C(2) pedicle and C(2) inferior articular process, the C(2) inferior articular process could be as a convenient key anatomic landmark to determine the location of C(2) pedicle and the position of C(2) pedicle screw entry point.
Ma
Xiang-yang
XY
Department of Orthopaedics, Guangzhou General Hospital of Guangzhou Military Command, Guangzhou 510010, China. maxy1001@sina.com
Yin
Qing-shui
QS
Wu
Zeng-hui
ZH
Xia
Hong
H
Zhong
Shi-zhen
SZ
Liu
Jing-fa
JF
Xu
Da-chuan
DC
D001368:Axis, Cervical Vertebra / Q000033:anatomy & histology* / Q000601:surgery; D006801:Humans; D013123:Spinal Fusion / Q000379:methods