Abstract
Objective: Fatty infiltration of paraspinal muscle is associated with spinal disorders. It can be assessed qualitatively (i.e., Goutallier classification) and quantitatively using image processing software. The aims of this study were to compare paraspinal muscle fatty infiltration as assessed using the Goutallier classification vs. quantitative magnetic resonance images (MRI) measurements and to investigate the association between anthropometric parameters and paraspinal muscle morphology and fatty infiltration in patients with symptomatic lumbar spinal stenosis (LSS).Methods: Patients affected by symptomatic LSS scheduled for surgery with available MRI of the lumbar spine were included in this retrospective cross-sectional study. Fatty infiltration at each lumbar level was rated qualitatively according to the Goutallier classification and quantified based on the cross-sectional area (CSA) of the paraspinal muscle, of its lean fraction (LeanCSA), and the ratio between LeanCSA and CSA and the CSA relative to the CSA of vertebral body (RCSA). Considering the muscle as a single unit, overall fatty infiltration according to Goutallier, overall CSA, LeanCSA, LeanCSA/CSA, and RCSA were computed as averages (aGoutallier, aCSA, aLeanCSA, aLeanCSA/aCSA, and aRCSA). Associations among parameters were assessed using Spearman's respective Pearson's correlation coefficients.Results: Eighteen patients, with a mean age of 71.3 years, were included. aGoutallier correlated strongly with aLeanCSA and aLeanCSA/aCSA (R = −0.673 and R = −0.754, both P < 0.001). There was a very strong correlation between values of the left and right sides for CSA (R = 0.956, P < 0.001), LeanCSA (R = 0.900, P < 0.001), and LeanCSA/CSA (R = 0.827, P < 0.001) at all levels. Among all anthropometric measurements, paraspinal muscle CSA correlated the most with height (left: R = 0.737, P < 0.001; right: R = 0.700, P < 0.001), while there was a moderate correlation between vertebral body CSA and paraspinal muscle CSA (left: R = 0.448, P < 0.001; right: R = 0.454, P < 0.001). Paraspinal muscle CSA correlated moderately with body mass index (BMI; left: R = 0.423, P < 0.001; right: R = 0.436, P < 0.001), and there was no significant correlation between aLeanCSA or aLeanCSA/CSA and BMI.Conclusions: The Goutallier classification is a reliable yet efficient tool for assessing fatty infiltration of paraspinal muscles in patients with symptomatic LSS. We suggest taking body height as a reference for normalization in future studies assessing paraspinal muscle atrophy and fatty infiltration.
Highlights
Muscle impairment is an important component of spinal disorders
Yarjanian et al found a reduced functional cross-sectional area (CSA) of paraspinal muscles in patients with symptomatic LSS (sLSS) compared to asymptomatic individuals; the difference was not significant when compared to subjects with chronic low back pain (LBP) without evidence of lumbar spinal stenosis (LSS) [17]
We found that CSA and LeanCSA had a strong and LeanCSA/CSA had a weak correlation with body height
Summary
Muscle impairment is an important component of spinal disorders. muscle dysfunction can be considered both a cause and a consequence of low back pain (LBP) [1]—for instance, several studies have shown an association between fatty infiltration and the reduced cross-sectional area (CSA) of paraspinal muscles with chronic LBP [2,3,4,5,6,7]. To date, the contribution of compromised muscles to pain in spinal pathologies, such as facet arthropathy, disc degeneration, spinal stenosis, or deformity, is unclear. Paraspinal muscle fatty degeneration and atrophy have been reported in patients with LBP and disc herniation [10,11,12,13] or degenerative lumbar flat back [14]. In patients with disc herniation, muscle infiltration may be asymmetric and more pronounced on one side than the other [15]. Patients with lumbar spinal stenosis (LSS) or symptomatic LSS (sLSS) show increased muscle atrophy and fatty infiltration [17]. While there are several studies investigating the correlation of muscle composition and morphology in patients with LBP, to date, evidence for this relationship in patients with LSS is lacking
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