Spinal Anatomy…and Scoliosis!
Written by Emma Yuguchi
Your spine is extremely complex and in fact – pretty remarkable!
Throughout my scoliosis journey, I was intrigued at the amazing complexity of the spine. Although scoliosis can sometimes be confusing, it was fascinating to learn a little bit more about the backbone of my body.
I remember seeing lots of x-rays and 2-D (flat) pictures, so it was really cool the few times when the doctor pulled out a 3-D model of a spine. You may have even seen a model when you walked into your orthopedist’s office. It really was interesting seeing something I could turn around and touch and see the different parts of the spine!
The Anatomy of a Spine
The vertebral column is a fancy way of saying your spine. You may have heard of the metaphor of something along the lines of: “you are the backbone of the team!” This is exactly what your spine does: it strengthens and supports your whole body.
All of our spines have three main functions:
- To support your head and provide structure to your body.
- To protect the spinal cord and nerves.
- To give you flexibility (when bending down, twisting, etc).
The spine is composed of alternating disks stacked on top of each other. The boney parts are called vertebrates. The squishy parts in between them are intervertebral discs that act like a cushion between the bones, made of a soft substance called fibrocartilage. Your spinal cord goes in the gaps near the middle of each vertebrae in an opening called the vertebral canal. Your spinal cord is about the thickness of your thumb, and is super important – it’s like the spine is providing a protective case.
First picture source: www.spineuniverse.com/anatomy; Second picture source: Human Anatomy Laboratory Manual (Heartline), bio.libretexts.org
The spine is generally divided into 4 regions. Each vertebrae is labeled from its corresponding section (for example, starting at the top vertebrae would be C-1. The uppermost vertebrae in the thoracic section would be T-1. The bottom most vertebra would be L-5).
Cervical: 7 vertebrae. This makes up your neck, and connects to your skull. The first vertebrae, called the atlas, allows you to move your head in a “yes” motion. The second vertebrae, called the axis, allows your head to move in a “no” motion.
Thoracic: 12 vertebrae. This is the longest section. Each vertebrae gets larger in size as you go down, and this section supports the ribcage and other parts of the body.
Lumbar: 5 vertebrae. These are the largest vertebrae, at the small of the back. They are largest because they need to support the weight of your upper body.
Sacral: This is a triangular structure that forms the base of the vertebral column. This connects the spine and the hips.
Coccyx: Also known as the tailbone.
Scoliosis
When viewed from the side, the spine has a natural S shape. This acts like a coiled spring to help your body absorb shock and it also keeps your body balanced.
If you have an abnormal curve of the upper curve, it is called hunchback. If there is an abnormal curve in the lower curve, it is called sway back.
From looking at the back, the spine is normally in a straight line. When curves side to side occur, it is called scoliosis.
Picture source: Al Fajr Physiotherapy and Rehabilitation Centre
Instead of having an “I” shaped spine, it can look like a “C” or an “S”.
In most cases you can visually see a curve, but one thing that I have always wondered is – how do you measure the actual degree? Well, you’ve got to use a little bit of geometry. The most common method used is called the Cobb Angle.
Most often, you start off with an x-ray scan. This shows the bones in a flat image. Remember, each vertebrae looks like a disc. On an x-ray they are like little rectangles.
Picture source: uptodate.com
First, you find the two most angled vertebrae. These are the two rectangles that if you were to draw parallel lines through them, would be the most tilted lines. One vertebrae is above the curve (called the superior vertebrae), and one is below (the inferior vertebrae).
Extend the line from the top of the superior vertebrae (line in red) and the bottom of the inferior vertebrae (line in blue).
Next, 90 degree lines are drawn from the two lines and intersected. It’s a bit confusing, but the vertical angle of these two lines is the measurement for the curve!
Sometimes MRI (magnetic resonance imaging) and CT (computed tomography scan) are used instead or in addition to an x-ray. This can provide a 3D image of soft tissues like the intervertebral discs and nerves (by MRI) and boney anatomy like partially formed or fused vertebrae (by CT). This can be used to determine some causes of scoliosis.
Types of Scoliosis
There are four types of scoliosis:
Congenial: When misalignment occurs due to deformed vertebrae or ribs at birth.
Idiopathic: Unknown cause. In some cases, genetics plays a role.
Neuromuscular: This is when the spine is affected by the surrounding muscles which affects development. Many factors can influence this type such as diseases affecting the spine.
Degenerative: This type affects those generally over 65 and is due to wear and tear from age. While everyone’s spine naturally degenerates overtime, it can affect some more than others leading to misalignment.
Wearing a Brace
Some of us have experienced wearing braces to correct our scoliosis. There are many different types of braces such as nighttime and full time braces. The brace works to exert corrective forces on the spine. It releases forces on the inner side of the spine, and increases forces on the outer part of the spine.
Source: spine-health.com
Many times adolescents and young kids are required to wear a brace so that while they grow the spine does not continue to develop in a curve. The brace is often weaned out after skeletal maturity because at that point your bones stop growing so the scoliosis will not progress. If an adolescent or adult is near or at skeletal maturity, the brace will not be as effective. In these cases, surgery is sometimes required.
Surgery
Surgery is done to correct severe scoliosis or scoliosis that cannot be corrected from a brace.
Oftentimes, a posterior approach is taken, which means that the surgeon goes through the back and fuses a few vertebrae together where they are curved. A rod is inserted to straighten the spine while the spinal fusion takes effect.
Image from: kidshealth.org
An anterior approach can also be used, which is where the surgeon goes through the side of the patient to get to the spine.
A decompressive laminectomy is when parts of the roof of the vertebrae, called the laminae, are taken off to give more room for the nerves. Screws and rods can also strengthen areas of the spine during this spinal fusion process.
Conclusion
The complexity of your spine enables you to do everything you do – from the slightest movement of your finger to moving your body through a swimming pool.
The backbone is often used as a metaphor for courage and strength. So I hope understanding more about the mechanics of your back hopefully gives you more courage in your scoliosis journey!
References
“How to Measure a Scoliosis Curvature.” Scoliosis Reduction Center, 6 Sept. 2021, https://www.scoliosisreductioncenter.com/blog/how-to-measure-scoliosis-curvature.
Paul McAfee, MD. “Types of Scoliosis Braces.” Spine, Spine-Health, 8 Dec. 2016, https://www.spine-health.com/conditions/scoliosis/types-scoliosis-braces.
“Scoliosis Diagnosis & More – Free MRI Review.” Preferred Surgicenter – Chicago’s Spine & Orthopedic Experts, 6 June 2018, https://preferredsc.com/spine/disease/scoliosis/diagnosis/.
Shier, David, et al. “Skeletal System.” Hole’s Essentials of Human Anatomy & Physiology, McGraw-Hill Higher Education, Boston, MA, 2009, pp. 147–152.
“Spinal Anatomy Overview.” Scoliosis and Spine Associates, https://www.scoliosisassociates.com/anatomy-diagnosis-2/spinal-anatomy-overview/.
“Spine Anatomy, Anatomy of the Human Spine.” Spine Anatomy | Mayfield Brain & Spine, Cincinnati, https://mayfieldclinic.com/pe-anatspine.htm.
Sydney Moninger, OTA. “4 Types of Scoliosis and Their Interventions.” BTE, BTE Technologies, LLC, 10 May 2022, https://www.btetechnologies.com/therapyspark/4-types-of-scoliosis-and-their-interventions/.