Biomechanical Evaluation of Cervicothoracic Junction Fusion Constructs

Jakub Godzik, Jonathan F. Dalton, Eduardo Martinez-del-Campo, Anna G.U.S. Newcomb, Felix Dominguez, Phillip M. Reyes, Nicholas Theodore, Brian P. Kelly, Neil R. Crawford

Research output: Contribution to journalArticle

Abstract

Objective: We studied the effect of different cervicothoracic construct design variables on biomechanical stability in vitro. Methods: Six fresh-frozen human cadaveric spines (C5–T4) were used. After intact analysis, each specimen was destabilized and reconstructed, with all groups having 4.0-mm pedicle screws placed at T1–T3. The 2 hook-rod constructs included interlaminar hooks at C6 and C7, with either 3.5-mm or 4.0-mm rods (C6–T3). The 2 screw-rod constructs tested included lateral mass screws at C6 and C7, with either 3.5-mm or 4.0-mm rods (C6–T3). The 2 screw-connector-rod constructs tested included lateral mass screws at C6 and C7, with either 3.5-mm or 4.0-mm rods; 1 rod spanned C6-C7 with a connector to a second rod of the same size spanning T1–T3. Global (C6–T3) and intervertebral (C6-C7, C7-T1, T1-T2, and T2-T3) ranges of motion were compared for each construct. Results: In terms of global (C6–T3) stability, 3.5-mm versus 4.0-mm rod constructs were not significantly different, regardless of whether the construct was hook-rod, screw-rod, or screw-connector-rod. The hook-rod constructs provided less stability compared with the screw-rod and screw-connector-rod constructs in lateral bending (P < 0.04) and axial rotation (P < 0.001). The screw-rod constructs demonstrated a similar range of motion to that of the screw-connector-rod constructs, except for significantly less axial rotation at the C6-C7 level with 3.5-mm rods (P = 0.04). Conclusions: We found that the rod diameter of a construct does not appear to significantly influence the biomechanical stability of subaxial constructs. The screw-rod construct resulted in certain biomechanical advantages compared with the screw-connector-rod construct, and both were significantly superior to the hook-rod construct.

Original languageEnglish (US)
JournalWorld Neurosurgery
DOIs
StateAccepted/In press - Jan 1 2019

Keywords

  • Biomechanics
  • Cervical spine
  • Cervicothoracic junction
  • Instrumentation
  • Interlaminar hooks
  • Lateral mass screw
  • Pedicle screw
  • Range of motion
  • Rod diameter
  • Thoracic spine

ASJC Scopus subject areas

  • Surgery
  • Clinical Neurology

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  • Cite this

    Godzik, J., Dalton, J. F., Martinez-del-Campo, E., Newcomb, A. G. U. S., Dominguez, F., Reyes, P. M., Theodore, N., Kelly, B. P., & Crawford, N. R. (Accepted/In press). Biomechanical Evaluation of Cervicothoracic Junction Fusion Constructs. World Neurosurgery. https://doi.org/10.1016/j.wneu.2018.12.040