Craniocervical fixation with occipital condyle screws: biomechanical analysis of a novel technique.
METHODS
A human cadaveric biomechanical study comparing craniocervical fixation techniques.


OBJECTIVE
To quantitatively compare the biomechanical stability of a new technique for occipitocervical fixation using the occipital condyles with an established method for craniocervical spine fusion.


BACKGROUND
Stabilization of the occipitocervical junction remains a challenge. The occiput does not easily accommodate instrumentation because of access and spatial constraints. In fact, the area available for the implant fixation is limited and can be restricted further when a suboccipital craniectomy has been performed, posing a challenge to current fixation techniques. Occipital screws are also associated with the potential for intracranial complications.


METHODS
Six fresh frozen cadaveric specimens occiput-C4 were tested intact, after destabilization and after fixation as follows: (1) occipital plate with C1 lateral mass screws and C2 pars screws and (2) occipital condyle screws with C1 lateral mass screws and C2 pars screws. Specimens were loaded in a custom spine testing apparatus and subjected to the following tests, all performed under 50-N unconstrained axial preload: flexion, extension, lateral bending, and axial rotation at 1.5 Nm. The constructs were statistically compared with a one-way analysis of variance and compared with the intact condition.


RESULTS
Motions were reduced by approximately 80% compared with the intact condition for both configurations under all motions. There were no statistically significant differences in the range of motion (ROM) between the 2 instrumentation conditions. The mean values indicated decreased ROM with the novel occipital condyle screw construct in comparison with the standard occipital plate and rod system.


CONCLUSIONS
Craniocervical stabilization using occipital condyle screws as the sole cephalad fixation point is biomechanically equivalent with regard to the modes tested (ROM and stiffness) to the standard occipital plate construct.
Uribe
Juan S
JS
Department of Neurosurgery, University of South Florida, Tampa, FL, USA. juansuribe@gmail.com
Ramos
Edwin
E
Youssef
A Samy
AS
Levine
Nick
N
Turner
Alexander W L
AW
Johnson
Wesley M
WM
Vale
Fernando L
FL
D001268:Atlanto-Axial Joint / Q000601:surgery; D001269:Atlanto-Occipital Joint / Q000502:physiology / Q000601:surgery*; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000601:surgery*; D006801:Humans; D016268:Internal Fixators; D009777:Occipital Bone / Q000601:surgery*; D016059:Range of Motion, Articular / Q000502:physiology; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*