Associations between Paraspinal Muscle Morphology, Disc Degeneration, and Clinical Features in Patients with Lumbar Spinal Stenosis

OBJECTIVE: The purpose of this study was to examine the relationships between intervertebral disc degeneration in the lumbar spine, paraspinal muscle morphology, and clinical features in patients with lumbar spinal stenosis (LSS). METHODS: A total of 52 patients with LSS participated in this study. Magnetic resonance imaging was used to assess intervertebral disc degeneration at L4/5 and to measure the standardized cross-sectional areas (SCSAs) of the multifidus and erector spinae muscles. The intensity of low back pain (LBP) and lower limb pain, the level of disability, and the quality of life (QoL) were evaluated using patient-reported outcome measures. The associations between the image findings and clinical features, including the disability score, the pain score for low back pain, and the QoL score, were calculated using Spearman’s rank correlation coefficient. RESULTS: No associations were found between disc degeneration and clinical features. However, disc degeneration and the SCSA of the multifidus muscle (r=−0.38, P <0.01) and of the erector spinae muscle (r=−0.29, P=0.04) were significantly associated. Analysis of the associations between muscle morphology and clinical features found that the SCSA of the multifidus muscle was associated with LBP (r=0.31, P=0.03). CONCLUSIONS: These results suggest that there is some correlation between atrophy of the multifidus and pain intensity. Consequently, focusing on the CSA of the multifidus muscle may help to clarify the causes of LBP in patients with LSS. However, because of the cross-sectional nature of this study, causal relationships could not be determined and further research is needed.