The impact of cervical pedicle screws for primary stability in multilevel posterior cervical stabilizations.
METHODS
A total of 12 human cervical spines were tested in vitro in a biomechanical nondestructive set-up to compare the primary stability of different posterior cervical instrumentations after a bilevel corpectomy.


OBJECTIVE
To evaluate the primary 3-dimensional stability with special focus on the impact of cervical pedicle screws.


BACKGROUND
Cervical pedicle screw fixation gains popularity due to supposed higher stability. However, biomechanical studies are rare. Especially the impact of a combination of lateral mass and pedicle screws on stability in multilevel posterior stabilizations has not been evaluated until now.


METHODS
A total of 12 human cervical specimens were loaded with pure moments and unconstrained motion between C4 and C7 was measured. The specimen were tested in the intact state, all lateral mass screws (all LMS) from C4-C7, cervical pedicle screws (CPS) C4 and C7 left, LMS C4-C7 right, C5+C6 left, CPS C4+C7 bilateral, LMS C5+C6, and a anterior-posterior instrumentation (360°).


RESULTS
All instrumentations showed a higher stability compared with the intact state. No difference was found for uni- or bilateral applied CPS. The all LMS showed comparable stability than the CPS instrumentations.


CONCLUSIONS
From a biomechanical primary stability point it seems unnecessary to add CPS in a bilevel corpectomy model. If CPS are added, the unilateral application seems sufficient.
Department of Orthopedics and Traumatology, University Medical Center Mannheim, Mannheim, Germany.
René
R
Schmidt
Heiko
H
Koller
Hans-Joachim
HJ
Wilke
Joachim
J
Brade
Juliane
J
Zenner
Oliver
O
Meier
Luis
L
Ferraris
Michael
M
Mayer
D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D001863:Bone Screws / Q000009:adverse effects / Q000592:standards*; D002102:Cadaver; D002574:Cervical Vertebrae / Q000033:anatomy & histology / Q000502:physiology* / Q000601:surgery*; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000209:etiology* / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D016059:Range of Motion, Articular / Q000502:physiology; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D016474:Weight-Bearing / Q000502:physiology