Changes of the posterior paraspinal and psoas muscle in patients with low back pain: a 3-year longitudinal study.

Purpose: This study aimed to investigate the changes of the posterior paraspinal muscles (PPM) and psoas muscle in patients with low back pain (LBP) over time.
Methods: Patients with LBP who had a repeat lumbar MRI with a minimum of 3-years apart at a tertiary referral center were analyzed. MRI-based quantitative assessments of the PPM and the psoas muscle were conducted for the baseline and follow-up MRI. The cross sectional area (CSA), the functional cross sectional area (fCSA) and the fat area (FAT) were calculated using a dedicated software program. The fatty infiltration (FI,%) of the regions of interest was calculated. Differences between the 1st and 2nd MRI were calculated for all assessed muscular parameters.
Results: A total of 353 patients (54.4%female) with a median age of 60.1 years and BMI of 25.8 kg/m ² at baseline were analyzed. The mean time between the 1st and 2nd MRI was 3.6 years. The fCSA _PPM declined in both sexes significantly from the 1st to the 2nd MRI, whereas the FAT _PPM increased. In line with this result, the FI _PPM increased in both males (29.9%) and females (19.4%). Females had a higher FI _PPM and FI _Psoas than males in both MRIs. In females, no significant changes were found for the psoas muscle. The CSA _Psoas and fCSA _Psoas in males were significantly smaller in the 2nd MRI. With increasing age, a significant trend in a decrease in ∆FI _PPM was observed for both sexes.
Conclusion: The study revealed significant quantitatively muscular changes in males and females, especially in the posterior paraspinal muscles in only three years' time.
(© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)