Quantifying the effect of posterior spinal instrumentation on the MRI signal of adjacent intervertebral discs

Mary H. Foltz, Robert M. O’Leary, Diana Reader, Nicholas L. Rudolph, Krista A. Schlitter, Jutta Ellermann, Casey P. Johnson, David W. Polly, Arin M. Ellingson

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


STUDY DESIGN: Ex vivo porcine imaging study.

OBJECTIVES: Quantitatively evaluate change in MRI signal at the discs caudal to spinal fusion instrumentation. Individuals who receive posterior spinal instrumentation are at risk of developing accelerated disc degeneration at adjacent levels. Degeneration is associated with a loss of biochemical composition and mechanical integrity of the disc, which can be noninvasively assessed through quantitative T2* (qT2*) MRI techniques. However, qT2* is sensitive to magnetic susceptibility introduced by metal.

METHODS: Nine ex vivo porcine lumbar specimens were imaged with 3 T MRI. Fast spin-echo T2-weighted (T2w) images and gradient-echo qT2* maps were acquired, both without and with posterior spinal fusion instrumentation. Average T2* relaxation times of the nuclei pulposi (NP) were measured at the adjacent and sub-adjacent discs and measurements were compared using t tests before and after instrumentation. The size of the signal void and metal artifact were determined (modified ASTM F2119-07) within the vertebral body and spinal cord for both MRI sequences. The relationship between T2* signal loss and distance from the instrumentation was evaluated using Pearson's correlation.

RESULTS: There was no significant difference between adjacent and sub-adjacent NP T2* relaxation time prior to instrumentation (p = 0.86). Following instrumentation, there was a significant decrease in the T2* relaxation time at the adjacent NP (average = 20%, p = 0.02), and no significant difference at the sub-adjacent NP (average = - 3%, p = 0.30). Furthermore, there was a significant negative correlation between signal loss and distance to disc (r = - 0.61, p < 0.01).

CONCLUSIONS: Spinal fusion instrumentation interferes with T2* relaxation time measurements at the adjacent disc but not at the sub-adjacent discs. However, there is sufficient signal at the adjacent disc to quantify changes in the T2* relaxation time following spinal fusion. Hence, baseline MRI scan following spinal fusion surgery are required to interpret and track changes in disc health at the caudal discs.


Original languageEnglish (US)
Pages (from-to)845-851
Number of pages7
JournalSpine Deformity
Issue number5
StatePublished - Oct 1 2020

Bibliographical note

Funding Information:
The work was supported by the Scoliosis Research Society and the National Institutes of Health [K12 HD073945, K01 AR070894, 1S10OD017974, and P41 EB015894]. Acknowledgements

Publisher Copyright:
© 2020, Scoliosis Research Society.


  • Adjacent disc disease
  • Disc health
  • Image artifact
  • Metal artifact
  • Metal interference
  • Spinal fusion instrumentation
  • Intervertebral Disc Degeneration/diagnostic imaging
  • Postoperative Complications/diagnostic imaging
  • Artifacts
  • Animals
  • Swine
  • Diffusion Magnetic Resonance Imaging
  • Spinal Fusion/adverse effects

Center for Magnetic Resonance Research (CMRR) tags

  • NMC
  • BI

PubMed: MeSH publication types

  • Research Support, Non-U.S. Gov't
  • Journal Article
  • Research Support, N.I.H., Extramural


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