Dissecting Low Back Pain: Lumbar Disc Herniation

One of the most common reasons to have severe acute low back pain is a herniated disc. There are different ways to name this problem including, disc bulge, disc protrusion and disc extrusion which can sometimes cause confusion. All of these terms are all ways to describe the same problem, just different degrees of it and I will go over all of that in this post. I will also explain the mechanism of herniating a disc, how and why it happens, risk factors, as well as treatment and prognosis.

So what is a lumbar disc anyway?

The spine is made of bones that are named vertebral bones (vertebrae). The vertebrae are separated and cushioned by structures called intervertebral discs. As mentioned the discs are located between the vertebral bones and in simple terms act like shock absorbers. While the vertebrae are hard calcified material (like any other bones in the body), the discs are not. The disc is a softer structure made up of a cartilaginous outer wall made of concentric sheets of collagen fibers called annulus fibrosus and a jelly like semi liquid interior called nucleus pulposus. Imagine it like a jelly donut where the annulus fibrosis is the harder crust of the donut and the jelly is the nucleus pulposus.

How does the disc get injured?

Sometimes disc injury can result due to a sudden single excessive strain or injury (like lifting something excessively heavy, car accident, trauma, fall, etc.). More often though the discs get injured due to gradual age related wear and tear process. This is called disc degeneration or degenerative disc disease. Disc degeneration is common and happens to some degree in everyone. As this degeneration progresses, even a minor strain, bend or twisting movement can cause a significant disc injury.

What are the different kinds of disc injuries?

As already mentioned there are different kinds of disc injuries including annular tears, disc bulges, disc protrusions, and disc extrusions. Disc protrusions and extrusions are types of disc herniations while disc bulges are not. Lets go through each in more detail. An annual tear is exactly what it sounds like which is a tearing that happened in the annular wall (annulus fibrosus) of the disc. This can be due to degenerative wear and tear or can be due to a sudden acute injury. The disc with an annular tear may or may not be herniated at the same time. Now lets discuss the difference between a disc bulge and a disc herniation. Its actually quite simple. In a bulge the disc starts to bulge out evenly partly or all the way around its circumference and only involves the outer layer of the disc (the annulus fibrosus). The inner part of the disc (the nucleus pulposus) is not displaced. In a disc herniation there is disruption to the annulus and the nucleus both. The annular wall will have a crack or tear across it (could be small, could be large) and the content of the disc, the nucleus, will herniate through the crack/tear to the outside of the disc. There are two types of disc herniation. In a disc protrusion the tear in the annular wall is smaller compared to an extrusion with few cartilage rings torn and the amount of inner disc material that came out also smaller. In a disc extrusion the annular wall rupture is larger with all or most of the cartilage rings torn and a lot more inner disc material leaking out through the tear. Knowing what kind of disc injury has occurred can be important in determining treatment and prognosis. The following image shows examples of each.

Are there risk factors for disc injury?

There are certain known risk factor that can increase risk of disc injury and herniation. These include weight, genetics, and occupation. Those who are overweight or obese are at risk for disc injury due to the extra pressure and stress on the disc from excess weight. Certain occupations that are physically demanding and involve repetitive lifting, bending, pushing, pulling, and twisting are at greater risk of back and disc injury. Some predisposition to disc injury can be genetic and inherited in families.

Treatment and prognosis

When it comes treatment for disc injury think of it in terms of short term goals and long term goals because there is usually no quick way out of this. This is not a strain/sprain injury, the pain will be more intense and will likely last much longer. Therefore treatment can vary and will have different purposes and indications. Short term, the most important goal is pain relief and controlling the pain. This is typically achieved with the help of medications and injections. The type of injection used to treat pain from a lumbar herniated disc is a lumbar epidural steroid injection. Once the pain is under better control and more tolerable then the focus of treatment shifts to long term improvement and hopefully resolution of the problem. This is usually achieved with physical therapy and home exercise program. Sometimes injections may need to be repeated if pain worsens. Early surgical intervention may be warranted in certain specific situations (intractable pain or neurological deficits). Otherwise surgery is typically reserved as a “last resort” option in cases when pain does not resolve on its own and does not improve with less invasive means.