[A static mechanical comparison between two transarticular internal fixation techniques in the lower cervical spine].
OBJECTIVE
To compare static mechanical difference between two transarticular internal fixation techniques in the lower cervical spine.


METHODS
Ten fresh human cadaveric cervical spines were harvested. On one side, transarticular pedicle screws were placed at the C3-4, C5-6, and C7-T1 levels, and transarticular screws were placed on the other side. The screw insertion technique at each level was randomized for right or left. The starting point for transarticular pedicle screw insertion was located at the midpoint of the inferolateral quadrant of the lateral mass and the direction of the screw was about 50 degrees caudally in the sagittal plane and about 45 degrees medially in the axial plane, and the starting point for transarticular screw insertion was 1 mm medial to the midpoint of the lateral mass, aiming in a 15 - 20 degrees caudally and 35 - 40 degrees lateral position. After screw placement, each set of vertebral bodies were mounted in a custom jig for axial pullout testing using a servohydraulic testing machine. The load-displacement curves were obtained for each screw pullout.


RESULTS
The mean pullout strength for the transarticular pedicle screws was 668 N. This compares with 414 N for the transarticular screws (P < 0.05), but there was not significant difference statistically between different cervical levels (P > 0.05).


CONCLUSIONS
The static mechanical strength of transarticular pedicle screws is superior to the transarticular screws, and the transarticular pedicle screw fixation has the biomechanical feasibility of clinical application.
Liu
Guan-Yi
GY
Department of Orthopaedics, Ningbo Sixth People's Hospital, Ningbo 315040, China.
Xu
Rong-Ming
RM
Ma
Wei-Hu
WH
Sun
Shao-Hua
SH
Huang
Lei
L
Yin
Jiang-Wei
JW
Jiang
Wei-Yu
WY
D000328:Adult; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D002574:Cervical Vertebrae / Q000601:surgery*; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D016268:Internal Fixators; D008297:Male; D015203:Reproducibility of Results; D021801:Zygapophyseal Joint / Q000503:physiopathology / Q000601:surgery*