Intermittent pain in patients with chronic low back pain is associated with abnormalities in muscles and fascia.

We investigated the relationship between paravertebral muscles and perimuscular connective tissues of the thoracolumbar fascia region and the four types of pain in patients suffering from chronic low back pain. A total of 17 patients with chronic low back pain participated in this study. Ultrasound imaging method was used to measure the thickness and echogenicity of the paravertebral muscles and perimuscular connective tissues. The measurement site considered in this study was located lateral to the midpoint between L2-3 and L4-5 spines. In addition, age, gender, BMI, numerical rating scale and the short-form McGill pain questionnaire 2 (includes questions with respect to continuous pain, intermittent pain, neuropathic pain and affective descriptors) were used for assessment. Statistical analysis was performed using correlation analysis and multiple regression analysis. A significant association was observed between paravertebral muscle echogenicity at L2-3 and the numerical rating scale (r = 0.499), between paravertebral muscle echogenicity at L4-5 with numerical rating scale (r = 0.538) and intermittent pain (r = 0.594), and between perimuscular connective tissue thickness at L2-3 and numerical rating scale (r = 0.762). We observed that the factor influencing perimuscular connective tissue thickness at L2-3 and L4-5 was intermittent pain (β = 0.513, β = 0.597, respectively). It was also observed that some of the imaging findings were associated with age and BMI. In conclusion, we observed that paravertebral muscle echogenicity and perimuscular connective tissue thickness in patients with chronic low back pain were associated with pain, especially intermittent pain.