May 16, 2017 by spinalcare
To understand low back pain, you have to have start with the anatomy of the spine. Between every vertebra of the spine is an intervertebral disc which provides flexibility while absorbing load we put on our spine. (See Figure 1). A disc is comprised of an inner nucleus pulposus and an outer annulus fibrosus. Think of the disc like a jelly donut – the inside jelly of the donut is the nucleus pulposus and the outside of the donut is the annulus fibrosus. In a healthy spine, the jelly is contained within the donut, yet havoc arises when the jelly escapes the middle of the donut. A disc herniation occurs when the jelly is no longer contained inside the donut. When we disregard proper movement, correct posture, proper lifting, and maintaining a healthy weight, we are more susceptible to disc issues.
There are four general classes of a disc herniation determined by severity: bulge (stage 1), protrusion (stage 2), extrusion (stage 3), and sequestered fragment (stage 4) (Figure 2). A disc bulge is best described if you picture a s’more. Think of what happens to the marshmallow when two gram crackers are pressed together – the marshmallow bows outward. Back pain is often associated with a disc bulge (although research is starting to show this is less likely the case – but that is a discussion for our next post), whereas back and leg pain are often associated with a disc protrusion. A disc protrusion involves the jelly- like nucleus is pushing outwards, while still contained within the donut. A disc extrusion and sequestered fragment is a result of the jelly having gone outside of the donut; the jelly is still attached to the donut in a disc extrusion, yet in a sequestered fragment the jelly is no longer in contact with the donut.
A herniated disc does not necessarily equal pain. This is worth noting (and we will delve into this further in the second part of this post). Disc herniations are tricky; just because a disc herniation is shown on an MRI does not mean there is back pain or pain down the legs. In fact, a systematic review that analyzed 12 studies found no consistent association between low back pain and MRI findings, including disc herniation3. More on this in part 2 next month.
Generally, the more forces the intervertebral discs bear, the more susceptible they are to herniating (See Figure 3). When standing, the low back muscles activate, which keep you from falling over, yet the activation of those muscles alone cause a compressive force nearly two times your body weight on the discs of the low back. For an individual with a symptomatic disc herniation, standing will likely cause the symptoms to worsen. The use of a lumbar support pad when seated reduces the load onto the discs. A study conducted by Dr. Stuart M. McGill, a foremost expert on spine biomechanics, concluded the damaging movement leading to disc herniation is repeated lumbar flexion2. One time is okay, our bodies can handle it, but faulty movement over a long period of time our spine cannot handle.
How do you prevent disc herniations? Wine may get better with age, yet that cannot be said about intervertebral discs. As we age the integrity of the annulus fibrosus, or the outside part of the donut, decreases. A study, published in the American Journal of Neuroradiology, used 33 articles that reported imaging findings for over 3,000 asymptomatic individuals; the results were 37% of 20-year-old individuals and 96% of 80-year-old individuals1 had a disc herniation, yet showed no symptoms. While we cannot control our age, there are preventable measures we can make to prevent disc herniations and maintain a healthy and functional spine. The nucleus pulposus has a high-water content to resist compressive loads; therefore, you should stay hydrated, but the reason goes far beyond the hydrated cushion of the intervertebral disc. While one day of forgetting to bring your water bottle to work will not likely play a significant role in overall disc health, lifting improperly one time will. The proper way to lift is with your legs, using your hips, not your knees (See Figure 4). The proper way to pick something up from the ground, whether it be a marble or a heavy box, is to bend your torso forward, bend your knees, which creates a hinge at the hips, grab the object, and keep the object close to your body as you stand upright (See Figure 5). As indicated in Figure 3, there is nearly 11 times intradiscal pressure when seated with a slouched posture; there is an easy fix for that – sit up straight. Our back supports us, and when overweight there’s more to have to support. A healthy weight is a great way to prevent disc problems.
Knowing how the discs work and how your spine deals with the stress that we place upon it, we hope that you can be better prepared to support and protect the discs in the back. The stronger the core, the better the lifting technique and the less load we place upon the spine, the better protected we are, but no one is immune from disc issues. The good thing is that it probably doesn’t matter. Stay tuned to Part 2 of our series on disc herniations and why much of what we just discussed might have less of an impact on your pain than you think.