Paraspinal Muscle Remodeling in Patients With Unilateral Lumbar Disc Herniation

Lumbar disc herniation is the most common diagnosed degenerative pathology in the lumbar spine with a prevalence of 2 to 3% in the adult population. Unilateral lumbar disc herniation is characterized by compression or irritation of the lumbar nerve roots or dural sac by either protrusion, extrusion or sequestration of the nucleus pulposus, mostly in the posterolateral region. Compression or irritation of the lumbar nerve roots and dural sac can induce unilateral sensory and motor symptoms. Therefore, it is the principal cause of lumbar spinal surgery.

Different imaging studies have investigated asymmetry of the paraspinal muscles in patient with unilateral low back pain due to lumbar discus herniation. Both animal and human studies indicate a reduction in total muscle cross-sectional area, increased fat infiltration and fibrosis within the lumbar multifidus at the affected side.

Increased fat infiltration is clinically important because there is a correlation between the amount of intramuscular fat and lumbar muscle dysfunction. Not only fat infiltration correlates with lumbar dysfunction, also a lower multifidus cross-sectional area is associated with and predictive for low back pain. This indicates that there is an association between paraspinal muscle changes/ remodeling and muscle dysfunction that could lead to low back pain.

The aim of this research is to quantify the decrease in muscle and muscle fibre size, the amount of fat infiltration, and the amount of fibrosis present within the multifidus muscle at the herniated side in relation to the unaffected side. The second aim is to investigate the possible role of different cell types in the process of muscle remodeling. The last aim of this study is to correlate these muscular changes with long-term functional outcomes such as pain, fear and disability. This information can possibly contribute to the etiology of paraspinal muscle changes, and provide a handgrip to future research.