gms | German Medical Science

63rd Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Japanese Neurosurgical Society (JNS)

German Society of Neurosurgery (DGNC)

13 - 16 June 2012, Leipzig

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Flexibility, cage loading and sagittal alignment in a defect model of the cervicothoracic junction

Meeting Abstract

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  • T. Pitzen - Wirbelsäulenchirurgie/Neurotraumatologie, SRH Klinikum Karlsbad Langensteinbach, Karlsbad
  • J. Drumm - Wirbelsäulenchirurgie/Neurotraumatologie, SRH Klinikum Karlsbad Langensteinbach, Karlsbad
  • B.A. Sharef - Wirbelsäulenchirurgie/Neurotraumatologie, SRH Klinikum Karlsbad Langensteinbach, Karlsbad
  • T. Welk - Radiologie, SRH Klinikum Karlsbad Langensteinbach, Karlsbad
  • C. Schilling - Biomechanisches Forschungslabor, Aesculap, Tuttlingen

Deutsche Gesellschaft für Neurochirurgie. Japanische Gesellschaft für Neurochirurgie. 63. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit der Japanischen Gesellschaft für Neurochirurgie (JNS). Leipzig, 13.-16.06.2012. Düsseldorf: German Medical Science GMS Publishing House; 2012. DocSA.09.04

doi: 10.3205/12dgnc365, urn:nbn:de:0183-12dgnc3655

Published: June 4, 2012

© 2012 Pitzen et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.

Outline

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Objective: Surgical treatment of defects within the cervicothoracic junction (CTJ) is often complicated by implant failure. The objective of the study was to analyse, how different implants influence flexibility, cage loading, and sagittal alignment within CTJ. This was done within an isolated anterior defect model of the CTJ.

Methods: 5 human cervical specimens C5-T2 were used with the following surgical modifications: Intact. Following application of an isolated anterior wedge-shape defect within C7 that was forced into failure by flexion-compression loading (Defect). Following vertebral body replacement and anterior plate fixation (Rigid Option of Quintex, Aesculap AG, Tuttlingen, Germany), ACDF. Following ACDF with dynamic loading (ACDF dyn). Following ACDF with pedicle-screw-rod fixation (S4, Aesculap AG, Tuttlingen, Germany), ACDF+Ped. We analysed in each surgical modification: 1. Three-dimensional (flexion-extension, left-right-lateral bending, axial left-right-rotation) flexibility C6–T1; 2. Cage loading during flexibilty test; 3. Lateral x-ray flexibility tests were performed using ±2.5 Nm pure moments in a custom spine tester. Cutting a standardised wedge shaped defect into the vertebral body C7 generated a defect. Failure was induced using a material test machine that applied loading in flexion-compression. Load to displacement graphs were recorded.

Results: Flexibility C6-T1, shown as an example in flexion-extension: Intact: 11.1°±3.5°, ACDF: 8.6°±3.5°, ACDF dyn: 9.4°±4.6°, ACDF+Ped: 5.8°±3.75°. (significant reduction only for ACDF+Ped versus intact, p=0.0497) Cage loading: ACDF and ACDF dyn allows peaks between loading and unloading. However, additional pedicle-screw- fixation (ACDF+Ped) reduces peaks significantly (p=0.003). Sagittal alignment C6-T1: Intact: Lordosis 2.1±5.3°, defect: Kyphosis 6.1±6.5°, ACDF dyn: Kyphosis 2.0±5.3°, ACDF+Ped: Lordosis 1.8±3.2°. Significant changes are noted for intact vs defect, ACDF Ped versus defect, ACDF+Ped vs. ACDF dyn, p=0.043, Wilcoxon Test.

Conclusions: Within this model, an anterior rigid plate does not reduce motility significantly versus the intact spine. Additional pedicle-screw rod fixation, however, does. Moreover, posterior fixation reduces peaks of loading and unloading and restores initial lordoctic alignment. Thus, an additional posterior fixation is useful to avoid implant failure, even if posterior elements are preserved.