Pull-Out Strength Comparison Among Conventional Pedicle Screw, Cortical Infero-Superior, and Cortical Supero-Inferior Trajectories in Yorkshire Porcine Lumbar Spines: A Biomechanical Study

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Figure 1
Trajectory proposed by the authors. (a) The screw insertional point. (b) Sagittal view of the screw after insertion for superior to inferior. (c) An axial cut of the screw trajectory to slightly lateral.
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Figure 2
Pedicle screw insertion with conventional trajectory.
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Figure 3
Pedicle screw insertion with cortical bone infero-superior trajectory.
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Figure 4
Pedicle screw insertion with cortical bone supero-inferior trajectory.
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Figure 5
Pull-out testing. The screw is connected to the insertion screwdriver in the apparatus that was designed to hold the vertebrae and the screw in line with the machine. The screw was then pulled out in the direction of the insertion.
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Figure 6
Maximum pull-out strength of the screws during pull-out testing. Pull-out strength was greater in the cortical bone infero-superior group. A statistically significant result was found only between the conventional and cortical bone infero-superior groups. Error bars indicate significant differences.