Morphological Changes in Paraspinal Muscles on MR Imaging in Chronic Low Back Pain Patients with Unilateral Lumbar Disc Herniation: A Cross-sectional Study

Abstract

Introduction: Low Back Pain (LBP) caused by Lumbar Disc Herniation (LDH) is a major cause of chronic disability worldwide. The management of LDH depends on clinical assessment and Magnetic Resonance Imaging (MRI) findings. Atrophy or fatty replacement of paraspinous muscles has a negative impact on the outcomes of both conservative and surgical treatment for LBP due to LDH. Aim: To analyse the morphological changes in paraspinous muscles using MRI in patients with chronic LBP and unilateral LDH. Materials and Methods: A cross-sectional study was conducted at Vardhman Mahavir Medical College and Safdarjung Hospital in New Delhi, India, from December 2020 to May 2022. A total of 59 patients, aged 21-65 years, with chronic LBP and unilateral LDH on MRI, were included in the study. The morphological changes in the Multifidus Muscle (MM) and Erector Spinae Muscle (EM) were analysed. The Cross-Sectional Area (CSA) of MM and EM, as well as the Signal Intensity (SI) of MM on the herniated side of the lumbar disc, were recorded and compared to the contralateral side at the same level. Continuous variables were expressed as mean±SD, median, and interquartile range, while categorical variables were presented as numbers and percentages. The Mann-Whitney test was used to compare continuous variables, and a p-value of <0.05 was considered statistically significant. Results: The mean age of the study participants was 39.17±12.82 years, with 59.3% male and 40.7% female participants. The CSA of MM on the side of disc herniation was 5.84±1.53 cm2 , compared to 6.52±1.69 cm2 on the unaffected side (p=0.02). The CSA of EM on the side of unilateral disc herniation was 13.08±3.04 cm2 , compared to 14.29±3.22 cm2 on the unaffected side (p=0.01). The SI of MM on the affected side was 175.84±100.99, compared to 147.70±83.50 on the unaffected side (p=0.02). Conclusion: Chronic LBP due to unilateral LDH resulted in a reduction in the Cross-Sectional Area (CSA) and fatty infiltration of the ipsilateral paraspinous muscles.