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What Muscles Are Affected In Scoliosis?

Muscles in Scoliosis

Scoliosis is a particular kind of spinal bend pattern in the body. It’s a complex condition with many different causes and a variety of expressions in the population. It can be present at birth, or caused by acute trauma, disease, and other factors. Because the spine is so central to our structure, scoliosis affects and is affected by many different muscles, both superficial and deep. In this article, we’ll take a brief look at the muscles most directly affected.

What is scoliosis?

Scoliosis refers to a condition of the spine where a section of the spine is laterally curving at least 10 degrees in the coronal plane. In this kind of pattern the spine is usually curving laterally and rotated. With this definition in mind, you might be able to think of many people you know whose small curves in the spine would be considered a scoliosis pattern. However, most of those incidences are mild and don’t require any treatment.

What causes scoliosis?

While some specific causes include various diseases, disorders, or physical traumas, most scoliosis patterns have no known cause. Specifically, there are congenital, neuromuscular, syndrome-related, idiopathic, and other reasons which cause scoliosis (Janicki et al., 2007). The most common kind has no known specific cause and is referred to as idiopathic scoliosis. Researchers think that the idiopathic type is most likely caused by some combination of genetic and environmental factors (Kim et al., 2009; Hermus et al., 2007).

In the case of idiopathic scoliosis, it’s a bit like the chicken and egg story. It’s possible for some environmental cause to result in a spinal curve which then affects the muscle tension balance around our spine and up and down the kinetic chain. And, it’s possible for activities, habits, injuries, and accidents to result in changes in muscle tension balance which results in a spinal curve. 

What does scoliosis look like?

It’s important when we think of scoliosis and muscles that we think three-dimensionally. Our spine moves in all three planes and in complex combinations of those planes. A scoliosis can similarly occur in all three planes or some combination of those. We commonly find for example some combination of a sidebend and a rotation in one or more sections of the spine. A scoliosis can have a single curve (referred to as a C-curve) or more than one curve.

Relationship between muscles and bones

One way to consider our body is as a tensegrity structure. Tensegrity is a design principle where tensional members maintain the positioning of structural members. In our body we could consider our bones to be structural members and our soft tissue to be tensional members. We have bones that are held in place by the tension of our soft tissue (muscles, fascia, and other connective tissue).

This means that there is a relationship between how our bones are positioned and how we’re holding tension in our muscles and fascia. So, muscle tension of spinal muscles on both the convex and concave sides of a spinal curve is affected by the position of the bones. Specifically, the spinal muscles are generally short and tight on the concave side and long and tight on the convex side of the curve.

Which muscles are most affected?

Basically, all the muscles that attach to the spine are directly affected by a scoliosis. More superficially we find muscles that attach to and move the spine like splenius capitis, splenius cervicis, and the erector spinae group, including iliocostalis, longissimus, and spinalis. At a deeper level, we find another layer of spinal muscles including the multifidus, rotatores, and semispinalis capitis. And at the very deepest layer of musculature next to the spine, we also have some very tiny muscles called the intertransversarii group which are located between adjacent transverse processes or adjacent spinous processes. They also contribute to spinal movement

We also have other deeper muscles which attach to the spine, but whose primary jobs are much broader than spinal movement. However, our spinal position still affects those muscles. Those include muscles like the quadratus lumborum, psoas major, and the diaphragm.

Other muscles affected

Indirectly you could imagine that the whole rest of the body is affected in some way when there is a lateral curve and/or rotation in the spine. The position of the head is affected because the spine is the base that our head sits on. So an imbalance in the spinal muscles would be reflected in the position and muscle tension at the head and neck. 

The position of the spine will affect the tension and shape of the abdominal container and associated muscles including the rectus abdominis, external obliques, internal obliques, and the transverse abdominis. The position of the spine also affects breathing-related muscles like the external and internal intercostals as well as the diaphragm which is directly affected by spinal position because it is attached to the spine.

You could also imagine that the shoulder girdle position would be affected by spinal position since our shoulders hang off of our torso. So differences in the tension of our shoulder girdle muscles could be indirectly affected by a scoliosis pattern. That could especially include muscles like the trapezius, latissimus dorsi, rhomboids, and serratus posterior.

Finally, the position of our spine will also have some effect on the position of our pelvis. So there will likely be some differences in tension in muscles on each side of the pelvis.

What is done to manage scoliosis?

Basic scoliosis treatment falls into three main categories. In the first doctors don’t actively apply any treatment. They observe to see if the condition worsens to the point that treatment is necessary. The second option is bracing to try to prevent the spinal curve from getting worse, particularly while children or adolescents are still growing. The third treatment is surgery to reduce the spinal curvature. More specific details on the causes and treatments of scoliosis are beyond the scope of this article.

Conclusion

Scoliosis is a lateral curve of the spine of 10 degrees or more usually combined with a rotation in the spine. Because our spine is so central to our body, a scoliosis affects our whole body in some way. The muscles most directly affected include all of the layers of spinal muscles from the most superficial to the deepest.

References 

Hermus, J.P.S., L.W. van Rhijn, and A. van Ooij. 2007. Non-genetic expression of adolescent idiopathic scoliosis: a case report and review of the literature. Eur. Spine J. 16(Suppl3):S338–S341.

Janicki, J.A. and B. Alman. 2007. Scoliosis: Review of diagnosis and treatment. Paediatr Child Health 12(9):771-776.

Kim, H.J., J. S. Blanco, and R. F. Widmann. 2009. Update on the management of idiopathic scoliosis. Current Opinion in Pediatrics. 21:55–64.

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