Special Poster Session 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

Pain-related patterns of multifidus fat infiltration are spatially distinct from age-related and BMI-related patterns of fat infiltration (#SP-7a)

Karim Khattab 1 , Lucas K Dziesinski 1 , Jessica Ornowski 1 , Jiamin Zhou 1 , Conor W. ONeill 1 , Noah Bonnheim 1 , Aaron J Fields 1 , Abel Torres-Espin 2 , Jeffrey C Lotz 1 , Jeannie F Bailey 1
  1. University of California San Francisco, San Francisco, CA, United States
  2. School of Public Health Sciences, Faculty of Health, University of Waterloo, Waterloo, Ontario, Canada

Introduction:

The paraspinal muscles (PSM) play a critical role in postural stability but are often degenerated, namely through fat infiltration (FI), in chronic low back pain (cLBP). While this is in part attributable to aging, degeneration of the PSMs has been found to associate with pain and adjacent degenerative disc pathologies, particularly in the multifidus (MF). A prior study has shown differences in the spatial distribution of FI in the multifidus between patients and controls. However, we do not know how age-related fat infiltration accumulates in the PSMs making it difficult to differentiate age-related degeneration from pathological changes to the PSM within cLBP patients. Understanding how these different factors affect PSM quality in cLBP patients may point towards the many underlying mechanisms of FI at play. To investigate this, we mapped the spatial distribution of FI in the multifidus at the L4L5 and L5S1 vertebral levels and assessed the association between spatial patterns of FI and confounding factors (age, sex, BMI). Then, accounting for age effects, we tested for differences in spatial patterns in FI associated with pain and disc degeneration.

 

METHODS:

From water-fat MR images of 40 axial cLBP patients, we examined the spatial distribution of PSM FI in relation to the center of rotation at the disc. Patients completed comprehensive pain and psychosocial surveying including pain intensity (0-10). Disc degeneration was scored using Pfirrmann Grade (PG). Using statistical parametric mapping (SPM) regression tests, we identified MF FI patterns associated with confounders (age, sex, and BMI), disc degeneration and pain intensity.

 

RESULTS:

The 40 patients (22F, 18M) had an average age of 54.9±14.2 years and average BMI of 25.7±4.3 kg/m2. FI was higher in the deep MF than the superficial MF at both levels; also, FI in the deep MF was elevated at L5S1 compared to L4L5 (Fig. 1A; p<.05). There were no differences in MF fat distribution between men and women or between right and left MF. At both levels, age correlated with elevated FI in the center of the MF (Fig. 1B-1C; p<.001) while BMI correlated with elevated FI localized to the superficial MF (Fig. 1B-1C; p<.05). After accounting for the effects of age on FI, pain intensity associated with MF FI in the deepest region of the MF (Fig. 1B-1C, p<.05). After accounting for age, disc degeneration did not associate with elevated FI anywhere in the MF.   

 

Discussion:

Our study identified age-related, BMI-related, and pain-related patterns of FI in the MF which appeared to be spatially distinct, affecting different regions of the MF. This suggests that cLBP associates with accelerated MF muscle degeneration outside of age-related and BMI-related mechanisms. Further, after accounting for age effects, disc degeneration severity did not associate with elevated FI anywhere in the MF, suggesting that prior findings of associations may be a result of natural muscle degeneration due to aging or age-related disc degeneration. Future work will investigate spatial patterns associated with psychosocial measures and specific disc pathologies linked to pain and will expand analysis to all lumbar levels.

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