Lumbar muscle structure and function in chronic versus recurrent low back pain: a cross-sectional study

Area of Science:

• Biomedical Engineering
• Musculoskeletal Imaging
• Pain Management

Background:

• Low back pain (LBP) presents significant heterogeneity, with distinct clinical pictures for recurrent (RLBP) and chronic (CLBP) forms.
• Muscle degeneration, including atrophy and fat infiltration in paraspinal muscles, is implicated in LBP pathophysiology.
• Existing research often overlooks the specific differences between RLBP and various forms of CLBP.

Purpose of the Study:

• To investigate differences in multifidus (MF) and erector spinae (ES) muscle structure and activity during trunk extension among patients with RLBP, non-continuous CLBP, and continuous CLBP.
• To evaluate muscle cross-sectional area, fat infiltration, and metabolic activity (T2-shift) in lumbar paraspinal muscles.
• To correlate muscle characteristics with LBP recurrence and chronicity.

Main Methods:

• Cross-sectional study involving 55 adults with non-specific LBP (24 RLBP, 15 non-continuous CLBP, 16 continuous CLBP).
• Magnetic Resonance Imaging (MRI), including T1-weighted Dixon scans for muscle structure (cross-sectional area, fat infiltration) and functional MRI for muscle activity during lumbar extension.
• Assessment of muscle cross-sectional area, lean muscle fat index, and T2-shift values for MF and ES.

Main Results:

• Continuous CLBP patients exhibited significantly higher fat infiltration (higher fat cross-sectional area and lean muscle fat index) in MF and ES compared to non-continuous CLBP and RLBP.
• No significant differences in total or muscle cross-sectional area were found between groups.
• RLBP patients showed a significantly lower T2-shift in MF and ES compared to non-continuous and continuous CLBP, indicating lower metabolic activity.

Conclusions:

• Continuous CLBP is characterized by increased fat infiltration in lumbar muscles without significant atrophy, distinguishing it from RLBP.
• RLBP is associated with lower metabolic activity in lumbar muscles, suggesting less intense muscle contractions.
• Non-continuous CLBP appears intermediate, sharing muscle structure similarities with RLBP and muscle function similarities with continuous CLBP, underscoring the distinct muscle profiles across LBP subtypes.