Paraspinal Muscle in Chronic Low Back Pain: Comparison Between Standard Parameters and Chemical Shift Encoding‐Based Water–Fat MRI

Abstract

Background Paraspinal musculature (PSM) is increasingly recognized as a contributor to low back pain (LBP), but with conventional MRI sequences, assessment is limited. Chemical shift encoding‐based water–fat MRI (CSE‐MRI) enables the measurement of PSM fat fraction (FF), which may assist investigations of chronic LBP. Purpose To investigate associations between PSM parameters from conventional MRI and CSE‐MRI and between PSM parameters and pain. Study Type Prospective, cross‐sectional. Population Eighty‐four adults with chronic LBP (44.6 ± 13.4 years; 48 males). Field Strength/Sequence 3‐T, T1‐weighted fast spin‐echo and iterative decomposition of water and fat with echo asymmetry and least squares estimation sequences. Assessment T1‐weighted images for Goutallier classification (GC), muscle volume, lumbar indentation value, and muscle‐fat index, CSE‐MRI for FF extraction (L1/2–L5/S1). Pain was self‐reported using a visual analogue scale (VAS). Intra‐ and/or interreader agreement was assessed for MRI‐derived parameters. Statistical Tests Mixed‐effects and linear regression models to 1) assess relationships between PSM parameters (entire cohort and subgroup with GC grades 0 and 1; statistical significance α = 0.0025) and 2) evaluate associations of PSM parameters with pain (α = 0.05). Intraclass correlation coefficients (ICCs) for intra‐ and/or interreader agreement. Results The FF showed excellent intra‐ and interreader agreement (ICC range: 0.97–0.99) and was significantly associated with GC at all spinal levels. Subgroup analysis suggested that early/subtle changes in PSM are detectable with FF but not with GC, given the absence of significant associations between FF and GC (P‐value range: 0.036 at L5/S1 to 0.784 at L2/L3). Averaged over all spinal levels, FF and GC were significantly associated with VAS scores. Data Conclusion In the absence of FF, GC may be the best surrogate for PSM quality. Given the ability of CSE‐MRI to detect muscle alterations at early stages of PSM degeneration, this technique may have potential for further investigations of the role of PSM in chronic LBP. Level of Evidence 2 Technical Efficacy Stage 2

Editorial on Special Issue “Spine Imaging: Novel Image Acquisition Techniques and Analysis Tools”

“…In addition to the fat quantification of vertebral BM, the CSE-MRI-derived PDFF has recently also been used to evaluate paraspinal muscle fat content [ 14 , 15 , 16 ]. For the degenerative spine, it has been shown that paraspinal muscle PDFF may be associated with lumbar back pain (LBP) and that cartilage endplate damage could be predictive of LBP when adjacent to paraspinal muscles with higher fat content [ 14 , 15 ].…”

“…In addition to the fat quantification of vertebral BM, the CSE-MRI-derived PDFF has recently also been used to evaluate paraspinal muscle fat content [ 14 , 15 , 16 ]. For the degenerative spine, it has been shown that paraspinal muscle PDFF may be associated with lumbar back pain (LBP) and that cartilage endplate damage could be predictive of LBP when adjacent to paraspinal muscles with higher fat content [ 14 , 15 ]. Furthermore, anatomical variations in PDFF for paraspinal muscles have been explored in relation to gender and body mass index (BMI), demonstrating associations for PDFF values between segments of the erector spinae muscles at the lower thoracic and lumbar spine (T9-T11, T12-L2, and L3-L5) [ 16 ].…”

Editorial for “Paraspinal Muscle in Chronic Low Back Pain: Comparison Between Standard Parameters and Chemical Shift Encoding‐Based Water–Fat MRI”

“…In this issue of JMRI , the manuscript by Sollmann et al investigated the utility of chemical shift encoding‐based water–fat MRI (CSE‐MRI) in quantifying the fat fraction (FF) within the paraspinal musculature in 84 adults with chronic lower back pain 3 . The study is part of the greater Back Pain Consortium Research Program which aims at developing effective and personalized care for lower back pain patients 3 …”

“…CSE‐MRI is a common multiecho (in‐phase and out‐of‐phase) sequence that capitalizes on the different precessional frequencies of fat and water in the tissue and can produce homogeneous fat‐specific images. The resulting proton density FF maps can be used to directly quantify the amount of fat in a prespecified region of interest such as the rotator cuff or erector spinae muscles 3,4 . The MRI protocol in this study consisted of a T1‐weighted fast spin‐echo and a six‐point iterative decomposition of water and fat with echo asymmetry and least‐squares estimation (IDEAL) sequences.…”

“…In this issue of JMRI, the manuscript by Sollmann et al investigated the utility of chemical shift encoding-based water-fat MRI (CSE-MRI) in quantifying the fat fraction (FF) within the paraspinal musculature in 84 adults with chronic lower back pain. 3 The study is part of the greater Back Pain Consortium Research Program which aims at developing effective and personalized care for lower back pain patients. 3 CSE-MRI is a common multiecho (in-phase and outof-phase) sequence that capitalizes on the different precessional frequencies of fat and water in the tissue and can produce homogeneous fat-specific images.…”