Abstract
The persistence of back pain following acute back “sprains” is a serious public health problem with poorly understood pathophysiology. The recent finding that human subjects with chronic low back pain (LBP) have increased thickness and decreased mobility of the thoracolumbar fascia measured with ultrasound suggest that the fasciae of the back may be involved in LBP pathophysiology. This study used a porcine model to test the hypothesis that similar ultrasound findings can be produced experimentally in a porcine model by combining a local injury of fascia with movement restriction using a “hobble” device linking one foot to a chest harness for 8 weeks. Ultrasound measurements of thoracolumbar fascia thickness and shear plane mobility (shear strain) during passive hip flexion were made at the 8 week time point on the non-intervention side (injury and/or hobble). Injury alone caused both an increase in fascia thickness (p = .007) and a decrease in fascia shear strain on the non-injured side (p = .027). Movement restriction alone did not change fascia thickness but did decrease shear strain on the non-hobble side (p = .024). The combination of injury plus movement restriction had additive effects on reducing fascia mobility with a 52% reduction in shear strain compared with controls and a 28% reduction compared to movement restriction alone. These results suggest that a back injury involving fascia, even when healed, can affect the relative mobility of fascia layers away from the injured area, especially when movement is also restricted.
Highlights
The thoracolumbar fascia is a prominent anatomical structure in the dorsal trunk region whose role in chronic low back pain is increasingly recognized [1,2,3,4,5,6,7]
In a previous human cross-sectional study, we found that subjects with chronic “non-specific” low back pain (LBP) for more than 12 months had both an increase in thickness and a decrease in mobility of the thoracolumbar fascia measured with ultrasound, compared with subjects without LBP [6, 7]
Ultrasound measurement of subcutaneous and perimuscular fascia tissue thickness There was no significant difference in the thickness of dermis and superficial connective tissue (Zone 1) between groups (ANOVA, F(1,16) = 0.29, p = 0.60) (Fig 6)
Summary
The thoracolumbar fascia is a prominent anatomical structure in the dorsal trunk region whose role in chronic low back pain is increasingly recognized [1,2,3,4,5,6,7]. In a previous human cross-sectional study, we found that subjects with chronic “non-specific” LBP for more than 12 months had both an increase in thickness and a decrease in mobility of the thoracolumbar fascia measured with ultrasound, compared with subjects without LBP [6, 7]. We hypothesized that these structural and functional abnormalities of fascia in subjects with LBP could represent a fibrotic process resulting from an initial soft tissue injury involving fascia, followed by movement restriction that could be worsened by pain or fear of pain. Subjects with low back pain have abnormal motor control strategies that may be in part due to altered proprioceptive input [10], and the role of fascia in motor control feedback loops is poorly understood, there is evidence that pathological processes involving connective tissue can affect the behavior of overlying muscles [11]
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