Biomechanical evaluation of five different occipito-atlanto-axial fixation techniques.
METHODS
The stabilizing effects of five different occipitocervical fixations were compared.


OBJECTIVE
To evaluate the construct stability provided by five different occipito-atlanto-axial fixation techniques.


BACKGROUND
Few studies have addressed occipitocervical reconstruction stability and no studies to data have investigated anterior-posterior translational stiffness.


METHODS
A total of 21 human cadaveric spines were used. After testing intact spines (CO-C2), a type II dens fracture was created and five different reconstructions were performed: 1) occipital and sublaminar wiring/rectangular rod, 2) occipital screws and C2 lamina claw hooks/rod, 3) occipital screws, foramen magnum screws, and C1-C2 transarticular screws/rod, 4) occipital screws and C1-C2 transarticular screws/Y-plate, and 5) occipital screws and C2 pedicle screws/rod. Biomechanical testing parameters included axial rotation, flexion/extension, lateral bending, and anterior-posterior translation.


RESULTS
Pedicle screw fixation demonstrated the highest stiffness among the five reconstructions (P < 0.05). The two types of transarticular screw methods provided greater stability than hook or wiring reconstructions (P < 0.05). The C2 claw hook technique resulted in greater stability than sublaminar wiring fixation in anterior-posterior translation (P < 0.05). However, the wiring procedure did not significantly increase the stiffness levels beyond the intact condition under anterior-posterior translation and lateral bending (P > 0.05).


CONCLUSIONS
C2 transpedicular and C1-C2 transarticular screws significantly increased the stabilizing effect compared to sublaminar wiring and lamina hooks. The improved stability afforded by C2 pedicular and C1-C2 transarticular screws offer many potential advantages including a high rate of bony union, early ambulation, and easy nursing care.


CONCLUSIONS
Occipitocervical reconstruction techniques using C1-C2 transarticular screws or C2 pedicle screws offer biomechanical advantages compared to sublaminar wiring or lamina hooks. Pedicle screw fixation exhibited the highest construct stiffness among the five reconstructions.
Oda
I
I
Orthopaedic Biomechanics Laboratory, Union Memorial Hospital, Baltimore, Maryland, USA. odaitr@aol.com
Abumi
K
K
Sell
L C
LC
Haggerty
C J
CJ
Cunningham
B W
BW
McAfee
P C
PC
D000368:Aged; D001268:Atlanto-Axial Joint / Q000502:physiology / Q000601:surgery*; D001269:Atlanto-Occipital Joint / Q000502:physiology / Q000601:surgery*; D001696:Biomechanical Phenomena; D001858:Bone Nails; D001863:Bone Screws; D001864:Bone Wires; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*