Published in:
01-07-2015 | Experimental research - Spine
Cortical bone trajectory and traditional trajectory—a radiological evaluation of screw-bone contact
Published in: Acta Neurochirurgica | Issue 7/2015
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Background
Cortical bone trajectory (CBT), a relatively new technique for pedicle screw insertion in the lumbar spine, is believed to have equivalent pullout and toggle characteristics compared with the traditional trajectory (TT). It has been hypothesized that the new trajectory offers higher cortical bone contact with the pedicle screws and therefore has an improved anchoring property over the traditional trajectory where the screws are inserted into the vertebral body trabecular space. The aim of this study is to evaluate the pedicle screw-cortical bone contact between the two trajectories from a radiological standpoint.
Methods
Two hundred twenty-two patients with degenerative lumbar spine disease underwent computed tomography scanning. For each patient, axial slices of the L4 and L5 vertebra were cut in two planes, one horizontal to the pedicle representing the plane at which pedicle screws are inserted using the TT and another in a more caudo-cranial plane representing the plane at which pedicle screws are inserted using CBT. For each trajectory, a region of interest (ROI) was selected within the area in which the screws are inserted. A CT number (Hounsfield scale) was then calculated within each ROI to compare the bone density.
Results
The CT numbers within the ROI for CBT were constantly almost over four times higher than that for the TT, and there was a significant difference between the values (p < 0.0001).
Conclusions
This study has demonstrated that, with the cortical bone trajectory, the pedicle screws penetrate a region that is richer in cortical bone compared to when using the traditional trajectory. This is in keeping with previous hypotheses that the new trajectory offers higher cortical bone contact.