The anatomic study of clival screw fixation for the craniovertebral region.
OBJECTIVE
To study the anatomic parameters related to clival screw and establish reference data concerning the craniovertebral fixation technique.


METHODS
Morphometric measurement of the clivus and the surrounding anatomic structures were obtained on 41 dry bone specimens. Then, 2-D CT reconstruction of the craniovertebral region of 30 patients (19 men and 11 women, ranging in age from 20-64 years with an average age of 38.8 years) were performed to measure the safety range for a 3.5-mm screw placement. Nine entry points were evaluated. Finally, one male fresh cadaver specimen (age 46 years) was dissected to observe the craniovertebral region.


RESULTS
The clivus faces the basilar artery, the V ~ XII cranial nerves, the pons, and ventral medulla oblongata at its intracranial surface. The longitudinal diameter of extracranial clivus was 25.87 ± 2.64 mm. The narrowest diameter of the clivus was 12.84 ± 1.08 mm, the distance between the left and right hypoglossal canal was 32.70 ± 2.09 mm at its widest part. The distance between the left and right structures, the maximum value was 49.31 ± 4.16 mm at carotid canal, the minimum value was 16.54 ± 2.04 mm at the occipital condyle. The measurement of clival screws placement simulation via 2-D CT reconstruction images shows the maximum upper insertion angle of three components the optimal entry points, the candidate points, the limit entry points was 130.19°, 125.23° and 85.72°, and the total mean screw length was 7.57, 10.13 and 15.6 mm at the vertical entry angle, respectively.


CONCLUSIONS
Clival screw placement is a viable option for craniovertebral fixation. There is a safe scope for the screw length and angle of the screw placement. And, these parameters obtained in the present study will be helpful for anyone contemplating the use of clival screw fixation.
Department of Orthopaedic Surgery, Second Affiliated Hospital of Wenzhou Medical College, Wenzhou, People's Republic of China.
Wei
W
Ji
Xiang-Yang
XY
Wang
Hua-Zi
HZ
Xu
Xin-Dong
XD
Yang
Yong-Long
YL
Chi
Jian-Sheng
JS
Yang
Sun-Fang
SF
Yan
Jian-Wu
JW
Zheng
Zhong-Xiao
ZX
Chen
D000328:Adult; D001863:Bone Screws; D003388:Cranial Fossa, Posterior / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009777:Occipital Bone / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D011859:Radiography