Evaluation of trunk muscles in lumbar degenerative disease using magnetic resonance imaging T2 mapping: Association with computed tomography parameters and body composition.

Background: In lumbar degenerative diseases, degeneration occurs in spinal structures, including the paravertebral muscles (PVM) and psoas major (PM). Current methods for assessing muscle degeneration lack standardization and quantitative measures. MRI T2 mapping provides a qualitative assessment of muscle tissue, but its utility in evaluating PVM and PM remains unclear. This study aimed to measure PVM and PM T2 relaxation times and assess its utility for quantitative evaluation of muscle quality.

Methods: Sixty patients (30 males; mean age 70.0 years) who underwent surgery for lumbar degenerative diseases were included. T2 relaxation times of the PVM and PM were measured using preoperative MRI T2 mapping at the L4/5 level. CT numbers and cross-sectional areas (CSA) were obtained from preoperative CT scans. Skeletal muscle mass and phase angle (PhA) were assessed using bioelectrical impedance analysis. Correlations between T2 relaxation times and radiological and body composition parameters were evaluated using Spearman's rank correlation coefficient.

Results: Mean T2 relaxation times for PVM and PM were 68.4 ms and 56.8 ms, respectively. PVM T2 relaxation times exhibited a strong negative correlation with CT numbers (r = -0.824) and positively correlated with age (r = 0.466). Furthermore, PVM T2 relaxation times were negatively correlated with systemic skeletal muscle mass (r = -0.466) and PhA (r = -0.480). In contrast, PM T2 relaxation times showed no significant correlations with skeletal muscle mass and PhA.

Conclusions: This study suggests that MRI T2 mapping may be a useful non-invasive tool for the quantitative assessment of trunk muscle quality in patients with lumbar degenerative disease. The strong correlations observed between PVM T2 relaxation time and both CT values and systemic sarcopenia markers indicate its potential for evaluating paravertebral muscle health without radiation exposure. These findings may also contribute to a deeper understanding of sarcopenia in patients with spinal disorders.