The Effects of Axial Loading on the Disc and Motion Segment Relative to Disc Degeneration and Pain Using Novel MRI Biomarkers

  • Author / Creator
    Abdollah, Vahid
  • The underlying pathology of low back pain (LBP) is poorly understood. Although MRI is often used as a sensitive modality for depicting pathoanatomical abnormalities, it is often clinically inconclusive due to a lack of specificity. While most patients experience symptoms when the spine is loaded, MR imaging is usually conducted in a relaxed supine position. Loading may induce morphological changes in the spine. Therefore, to improve the specificity of MRI, one solution could be to apply loading using axial compression devices. This PhD investigated the response of the lumbar spine to compression and traction in participants with and without chronic LBP using MRI T2-mapping to identify imaging biomarkers holding promise for further investigation towards meaningful subgrouping of LBP or degeneration. Four studies informed the planning of the loading studies: 1) a systematic review of acute loading responses on imaging measurements of the disc and vertebrae to identify potential biomarkers, 2&3) two reliability studies of the novel candidate biomarkers measured using a novel semi-automated segmentation algorithm, and 4) a comparison of disc fluid content biomarkers’ responses to extension exercise. Finally, two pilot experimental studies were conducted to determine: 5) the relation between disc degeneration severity and effects of compression and traction on lumbar discs and vertebrae and 6) the effects of compression and traction on lumbar MRI findings in relation to chronic LBP. The systematic review illustrated a lack of comparisons of the response to loading between participants with and without pain and no studies on traction. The review identified 14 biomarkers; most did not detect effects of loading. However, limited evidences of forward shift in the nucleus, increased disc diameter, and decreased disc height were observed under compression. Since 50% body weight was commonly used in traditional MRI, it was adopted in this thesis. Twelve candidate biomarkers were chosen based on having detected changes in the review or representing novel measurements of fluid distribution postulated to be sensitive to loading: the location of the T2-weighted centroid (T2WC: mean position of the points in an ROI, weighted by their T2), and geometric weighted centroid (GWC: mean position of the points in an ROI, weighted based on their location), disc height, disc and nucleus mean T2 time and diameter, and motion segment angle. Reliability studies indicated that T2WC, GWC, and disc height using different disc width, presented excellent reliability. The novel measurements of fluid distribution showed a better ability to detect changes in response to extension exercises compared to mean signal intensity. Only the horizontal location of the disc T2WC detected significant differences immediately after exercise. The study of the relation between disc degeneration and response to loading indicated that smaller responses to loading correlated with more severe disc degeneration. Traction compared to compression was most sensitive to capture the load-induced changes in the lumbar spine. Disc height and diameter, disc and nucleus mean T2 time and T2WC, as well as, the nucleus GWC hold promise as sensitive biomarkers to capture loading responses. The study comparing loading responses between participants with and without LBP indicated that different responses to loading between groups were most often observed at L5-S1. The most sensitive biomarkers for pain were the horizontal-coordinate of the disc and nucleus T2WC (large effect sizes), the horizontal- and vertical-coordinates of the nucleus GWC, and the vertical-coordinates of the discs (small effect) and nucleus T2WC (moderate effect). These biomarkers hold promise for future investigation. In contrast, the nucleus’ width, the disc and nucleus mean T2 times, and disc width were least sensitive to capture pain-related differences. Four biomarkers showed the potential to detect pain-related differences by comparing a single supine unloaded scan. In the pain group, the disc T2WC and nucleus GWC between L3-4 and L5-S1 and nucleus T2WC at L4-5 were moderately to largely more anterior. Likewise, the disc height was taller at L3-4 and L4-5 by a large effect size. Because the response to loading of our proposed parameters was correlated to with degeneration and some loading responses of parameters detected differences related to pain grouping, our results justify further investigation of the clinical value of the proposed biomarkers. These biomarkers show promise to improve the specificity of MRI for LBP and the ability to detect the response to loading.

  • Subjects / Keywords
  • Graduation date
    Spring 2017
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.