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Cortical bone trajectory and traditional trajectory—a radiological evaluation of screw-bone contact

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Abstract

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.

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Acknowledgments

All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.

Conflicts of interest

None.

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Authors and Affiliations

  1. Spine and Spinal Cord Center, Mita Hospital, International University of Health and Welfare, 1-4-3 Mita, Tokyo, 108-8329, Japan

    Kota Kojima, Shunji Asamoto, Masayuki Ishikawa & Yasuyuki Fukui

  2. Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo, 160-8582, Japan

    Kota Kojima & Yoshiomi Kobayashi

Authors
  1. Kota Kojima
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  2. Shunji Asamoto
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  3. Yoshiomi Kobayashi
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  4. Masayuki Ishikawa
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  5. Yasuyuki Fukui
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Correspondence to Kota Kojima.

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Kojima, K., Asamoto, S., Kobayashi, Y. et al. Cortical bone trajectory and traditional trajectory—a radiological evaluation of screw-bone contact. Acta Neurochir 157, 1173–1178 (2015). https://doi.org/10.1007/s00701-015-2432-6

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  • DOI: https://doi.org/10.1007/s00701-015-2432-6

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