A cross-sectional study 1of the multifidus muscles (MM) and erector spinae muscles of 68 women and 42 men found significantly higher levels of muscles in subjects without disc herniation than in the disc herniation group, indicating that chronic pressure on the root of the spinal nerve may cause degeneration and atrophy of the MM and erector spinae muscles groups.

 

Single-Level Disc Herniation

Model of Single-Level Disc Herniation.

 

The Study

110 LBP patients with an average age of 40 were analyzed and divided into two groups—those with single-level disc degeneration, and those without disc degeneration. Subjects with multilevel degeneration were excluded, as were those with deformities of the spine or a history of spinal surgeries. Both groups were radiographed via MRI at the lumbar levels, and the imaging results were compared to examine the paravertebral muscles, disc heights, and perpendicular distances between the laminae and MM. Statistical analysis using software compared the variables using the Kolmogorov-Smirnov test to investigate data distribution.

Results

The LBP patients without lumbar disc herniation had clinically-significant greater MM and erector spinae muscles than those with radiographically-confirmed disc degeneration. No significant differences existed, however, in the disc heights, perpendicular distances between the MM and the laminae, or the psoas major cross-sectional areas of the two study groups.

Discussion

The MM stabilizes the lumbar spine and, when negatively impacted, contributes to LBP. The muscle group create more force over a smaller range than the longer spine muscle groups, which helps to stabilize movement. The dorsal rami of the spinal nerves stimulates the MM and erector spinae, but the psoas major is stimulated by ventral rami lumbar spinal branches, prior to their joining the lumbar plexus. The medial paraspinal muscles are stimulated from one nerve root, but the iliocostalis and longissimus muscles receives stimulation from many roots. Indications of muscle degeneration include decreased muscle size and increased fat deposits in the area.

Because the MM and erector spinae are stimulated by the dorsal root stemming from a singular level, the chronic and long-lasting pressure on the root due to disc herniation contributes to the degeneration and atrophy of these muscles. This atrophy is not evident in the psoas muscle because it is stimulated by the nerves of many different levels, rather than a singular source. In order for muscle atrophy to occur, there must be at least six weeks of compression, according to this study’s authors.

Conclusion

Evidence of increased fatty deposits and decreased muscle in a cross-sectional lumbar image indicates the existence of muscle degeneration in LBP patients, assuming there has been at least six weeks of compression on the MM or erector spinae muscle groups, which are stimulated by a single nerve root.

 

KEYWORDS: Muscle Degeneration in LBP Patients with Single-Level Disc Herniation, single-level disc degeneration, paravertebral muscles, disc heights, and perpendicular distances between the laminae and MM, pressure on the root due to disc herniation contributes to the degeneration and atrophy of these muscles

  1. Volumetric Muscle Measurements Indicate Significant Muscle Degeneration in Single-Level Disc Herniation Patients
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