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68th Annual Meeting of the German Society of Neurosurgery (DGNC)
7th Joint Meeting with the British Neurosurgical Society (SBNS)

German Society of Neurosurgery (DGNC)

14 - 17 May 2017, Magdeburg

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CT-morphometric-analysis of C2 to evaluate the "safety zones" for anterior transarticular screw plaecements

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  • Rebecca Leyrer - Universitätsklinikum Essen der Universität Duisburg-Essen, Klinik und Poliklinik für Neurochirurgie, Essen, Deutschland
  • Nicolai El Hindy - Universitätsklinikum Essen der Universität Duisburg-Essen, Klinik und Poliklinik für Neurochirurgie, Essen, Deutschland
  • Oliver Gembruch - Universitätsklinikum Essen der Universität Duisburg-Essen, Klinik und Poliklinik für Neurochirurgie, Essen, Deutschland
  • Karsten H. Wrede - Universitätsklinikum Essen der Universität Duisburg-Essen, Klinik und Poliklinik für Neurochirurgie, Essen, Deutschland
  • Ulrich Sure - Universitätsklinikum Essen der Universität Duisburg-Essen, Klinik und Poliklinik für Neurochirurgie, Essen, Deutschland
  • Oliver M. Müller - Universitätsklinikum Essen der Universität Duisburg-Essen, Klinik und Poliklinik für Neurochirurgie, Essen, Deutschland

Deutsche Gesellschaft für Neurochirurgie. Society of British Neurological Surgeons. 68. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), 7. Joint Meeting mit der Society of British Neurological Surgeons (SBNS). Magdeburg, 14.-17.05.2017. Düsseldorf: German Medical Science GMS Publishing House; 2017. DocP 064

doi: 10.3205/17dgnc627, urn:nbn:de:0183-17dgnc6275

Published: June 9, 2017

© 2017 Leyrer et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.

Outline

Text

Objective: To measure anatomical variations in critical passages of C2 for the placement of anterior transarticular screws through C1/C2 compared to odontoid and posterior screw placement.

Methods: 50 CT data volume scans of the cervical spine were anonymously analyzed with a total of 750 measurements of C2. Angulation of the entry trajectories were assessed as well as 14 bilateral defined distances that allow to define „safe entry“ zones for the screws and their passages either into the odontoid process or transarticular through C1/C2.

Results: The angulation for an odontoid screw placement is much shallower than for the transarticular passages (24.9° vs. 39.1° and 40.5°, respectively) allowing screw placement easier even in short-neck or barrel-thoraces. While the isthmus of C2 was as narrow as 4.1mm (r) and 4.2mm (l) on average, respectively, the anterior entry zone for screw placement was between 9.7mm (r) and 10mm (l) with a length distance of 7.8mm (r) and 8mm (l) towards the vertebral artery. Length of the massae laterales was approximated with 14.6mm (r) and 14.3mm (l).

Conclusion: Our data show that the trajectory employed for transarticular screw fixation of C1/C2 is much steeper than for odontoid screw placement, suggesting a more convenient application especially in short-necked and/ or high BMI patients. The „safety zones“ in our series are more generous for the anterior screw placement with respect to the course of the vertebral artery compared to the passage of posteriorly placed screws. Hence, from an anatomical point of view the anterior transarticular screw placement bears more convenient and safer routes for the implants than the odontoid screw placement of posterior fixation.