Quantifying the effect of posterior spinal instrumentation on the MRI signal of adjacent intervertebral discs
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Quantifying the effect of posterior spinal instrumentation on the MRI signal of adjacent intervertebral discs Mary H. Foltz1 · Robert M. O’Leary2 · Diana Reader2 · Nicholas L. Rudolph2 · Krista A. Schlitter2 · Jutta Ellermann3 · Casey P. Johnson4,5 · David W. Polly Jr.6 · Arin M. Ellingson1,2,6 Received: 23 November 2019 / Accepted: 11 May 2020 © Scoliosis Research Society 2020
Abstract Study design Ex vivo porcine imaging study. Objectives Quantitatively evaluate change in MRI signal at the discs caudal to spinal fusion instrumentation. Summary of background data 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
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