Herniated Disk in the Lower Back

As the name suggests, the intervertebral discs are the parts between vertebra. The backbone or spine, is also known as the vertebral column. It is made up of a bunch of cylinder-like bones called vertebrae, each stacked on top of one other. There are 33 bones to be exact, but some of them are fused or united together.

The vertebra which are not fused together are separated by a jelly or sponge-like material called a disc. The discs between the vertebrae (ie. Intervertebral discs), are where all the movement comes from in your spine. There are only 23 intervertebral discs in the spine and each one can allow some degree of movement. 

The discs are commonly referred to as spongy or jelly-like material. However, they should really be described as having two concentric layers; a soft inner layer and a tough outer layer. Some people describe them as a doughnut with a jelly like material on the inside and a tougher ‘bread’ layer on the outside.

However, it may be easier to think of them like oranges. The outer layer of a disc is a tough material called the annulus fibrosus which is made up of 25 or more layers of very tough collagen sheets, similar to the peel of an orange and the material of your skin.

The outer layer attaches to the vertebra bone above and below, and keeps all the anatomy in place, including the inner pulp and liquid. The inner layer of a disc is made up of a soft jelly-like material called the nucleus pulposus (yes, its like the pulp of an orange but softer).

Normally, the outer tough sheet layer (ie. Annulus fibrosus), keeps the nucleus pulposus inside, just like how the outer peel of an orange protects the inner fruit. As long as the annulus fibrosus is intact, there are very few problems with the disc. However, when you have a ‘tear’ in this outer disc layer (ie. Annular fissure), this is when the inner nucleus pulposus ‘herniates’ out and becomes a problem.

It can start off as a ‘contained’ fissure just within the inner layers of the annulus fibrosus. But overtime, can spread so that the tear breaks through all layers of the annulus and allows the inner nucleus pulposus to ‘herniate’ outwards onto the surrounding nerves. 

They provide two important functions. First, this is where all the movement comes from in your spine. The bones don’t change shape when you bend forward or to the side, instead your discs change shape and become ‘wedged’. This allows the vertebral bones and therefore the spine, to move in a wide variety of directions.

The second function is to absorb impact forces and provide stability. When you run or sit in a bumpy car-ride, you are constantly loading the spine with different ‘axial’ and shear forces. To help reduce some of those pressures, the disc can absorb them like a sponge.

The inner nucleus pulposus absorbs pressure forces, while the annulus fibrosus holds the bones and jelly-like nucleus pulposus in their places. However, when the disc becomes ‘worn-out’ or degenerative, those pressures are no longer easily absorbed and so they are then distributed to the surrounding joints and ligaments, resulting in increasing back pain and strain. 

There is no specific classification for disc herniations. Instead we classify them according to their shape and location. The majority of all disc herniations tend to occur within the lumbar (lower back) and cervical (neck) region. When we describe their shape, we can use terms like ‘broad’, ‘sequestered’, or protruded to describe their shape. On the other hand when we describe their location, we are commenting on where the disc is herniating in relation to the vertebra’s bony landmarks.

Normally, the discs change shape to allow for movement between each of the spine bones (ie. Vertebra).  They can change into a wedge shape or ellipsoid shape, but should always change back to their normal shape. When a disc ‘bulges’, this means that the annulus fibrosis (ie. The outer layer of the disc), sticks out further than the margins of the bone.

Normally, discs tend to bulge all the time when they are loaded, but should always revert back, like an elastic band. Its typical for a disc to bulge 25% or greater when we are performing movements like bending our back or twisting to the side. However, over time and with aging, the discs become less stretchy, just like our skin. As a result, the disc do not revert back to their normal position but stay in a ‘bulging’ shape. As the amount of the bulge increases, it can sometimes push on the nerves sitting alongside the disc.

A disc herniation is when a small area of a disc bulges outwards. Unlike a disc bulge, which is broad and involves a large circumference of the disc, a herniation only involves a quarter of the disc circumference. Normally, whether there is a disc herniation or bulge, the margins of an intervertebral disc should not stay beyond the bone edges; they should return back to their normal position when the spine becomes relaxed. It is normal for a disc to ‘bulge’ with certain movements. However, when a disc herniates, a specific small area of the entire disc is bulging. 

A bulging and herniated disc imply the same problem; part of the disc is sticking out beyond its normal margins of the bone above and below the disc. The main difference is the shape; a herniation is a focal small area of bulging disc, less than one-fourth of the circumference of the disc.

While a disc bulge, involves a larger disc area. We distinguish between them because they suggest two different underlying problems. In the case of a disc bulge, the problem tends to be due to a loss of elasticity. For this reason it is commonly seen in more elderly patients and due to the inability of the disc to spring back into position when it is loaded with a force or weight.

On the other hand, a disc herniation suggests that a specific area of the disc (specifically the annulus fibrosus layers), has a tear or weakness in it so that it bulges out along that area. A herniation can occur at any age group, but tends to be the more common type among younger patients. 

A sequestered disc is when a herniated disc material breaks into fragments. Normally, the inner jelly like material (ie. Nucleus pulposus), stays together when it herniates out. However, sometimes, the herniated material breaks off into little fragments or pieces.

This is important because a sequestered disc herniation has a much better change of resolving on its own without the need for surgery. The reason for this is that when the disc is altogether, that chances of the body absorbing it and removing it is less than if it was already fragmented. Just like when you cut a piece of steak into several small pieces.

When a disc is said to have ‘migrated’, this means that it is no longer herniated at the level of the disc. Instead it has sequestrated and traveled beyond the margins of the normal disc and is not sitting behind the upper or lower vertebral bone. Discs migrate because there is a lot of pressure from all the weight and forces acting on the spine.

Therefore, when there is a tear in the outer disc, the inner jelly-like material (ie. Nucleus pulposus) will herniate outwards. However, it can only herniate so far before it encounters nerve, bone, or other ligaments. As a result, it then has to either travel downwards or upwards, and is then said to ‘migrate’. 

A disc protrusion and extrusion are a type of herniated disc. The only difference between them is the shape. A protrusion is shaped like a bush from the ground; the bottom layers are wider than the top. A disc extrusion is the opposite and is similar to a tree; the end of the herniation is much wider than the closer base or ‘stem’.

The difference matters because they tend to represent 2 patterns of herniations. A disc protrusion is when all layers of the outer annulus fibrosus herniated outwards. On the other hand, a disc extrusion is when only the inner nucleus pulposus herniates through a tear in annulus fibrosus. 

Disc degeneration means that the discs are no longer made up of their normal components and begin to break apart. Normally, a spinal or intervertebral disc is made up of lots of proteins that attract water. In fact, it is typically made up of 80% water. As we get older, the type of proteins within the disc change and they hold less water.

This process is called ‘desiccation’ and can be thought of as dehydration where the water content of a disc is abnormally low. As a disc degenerates, it loses its ability to absorb shocks and forces travelling across the spine. As a result, the surrounding ligaments and joints of the spine have to carry a larger load and this leads to a lot of the symptoms of back pain.

The changes that occur when a disc degenerates can be seen on an MRI (magnetic resonance image), but not on an xray or CT scan. Instead, we ‘infer’ or assume disc degeneration on an X ray or CT scan based on other findings like loss of the normal space between the discs, or new bone formation around the discs called osteophytes.

Disc herniations almost always occur around the posterior (back) area of the spine. When the herniation is ‘central’ it occurs just in the middle. These are extremely uncommon due to the fact that there is a long tough ligament travelling along the center called the posterior longitudinal ligament (PLL).

Normally, this ligament is a check-reign strap which prevents a disc herniation from building into the spinal canal. The only time that this occurs is when the PLL is injured or has a tear in it. A paracentral or sub-articular herniation is the most common type and occurs when the herniation is between the center and the foramen area of the vertebra.

A transforaminal hernia occurs around the foramen area. The foramen area is alongside the facet joints and these herniations are problematic because in elderly patients their facet joints are quite degenerative and osteoarthritic.

This means that there will be less space than normal due to the arthritis, and when a disc takes up more of that space, it is easy to squeeze or pinch the nerve roots travelling through the foramen area. Lastly, any herniations which are extra-foraminal, occur outside of the foramen area. 

An annular fissure is basically a tear in the annulus fibrosus layer (ie. The outer layer of a disc). It means that some of the inner spongy layer (ie the nucleus pulposus), can squirt out through the torn fibers of the annulus fibrosus. Just like the pulp of an orange can squeeze through the outer peel. When you have a ‘tear’ in this outer disc layer (ie. Annular fissure), this is when the inner nucleus pulposus ‘herniates’ out and becomes a problem.

Remember the annulus fibrosus is made up of about 25 sheet layers. So a tear can start off on the inside as a ‘contained’ fissure, just within the inner layers of the annulus fibrosus, but overtime can spread so that the tear breaks through all approximate 25 sheet layers and allows the inner nucleus pulposus to ‘herniate’ outwards onto the surrounding nerves.

The intervertebral discs of the spine is where all your movement originates from. The joints in the back, also known as the ‘facet’ joints, control the direction in which the spine’s vertebral blocks can move (eg. forward, backwards, sideways, etc.), but the extent of movement is decided by the discs.

The spinal column is not a single long bone. Instead, it is made up of 34 blocks (ie. Vertebra), stacked on top of each other. Some of these blocks are fused together. Others blocks (ie. Vertebra) have discs between them which allow all movement. Remember, that bones cant change shape, so all movement in the body comes from your ‘joints’ in between those bones.

The spine is similar in that all movement comes from the joints between the spinal vertebral bones. When a disc is removed and the bones are fused, you still have movement in your spine from the levels above and below. However, those remaining levels may have to compensate.

On the other hand, when a discectomy is performed, the inner nucleus pulposus material is removed, but the outer annulus fibrosus layer is kept intact. By removing the nucleus pulposus, it then results in its replacement with type of scarred material known as fibrocartilage. This still allows movement within the disc, although its ability to absorb forces and impacts is much lower.

The finding of air within the disc space or a ‘vacuum phenomenon’ simply means that your disc is worn out and that there is excessive movement around that disc space. Normally, the disc maintains its shape and height, and the vertebral spine bones above and below the disc have very little movement, typically only 5 degrees of movement.

However, when the inner layer of the disc (ie. Nucleus pulposus) either degenerates or herniates, it leaves behind a void or space in the center. Then, due to excessive movement of the bones above and below, and especially when they are standing upright so that there is gravity pressure, that new void or space becomes compressed in between the two bones.

As a result, when a person lies down, that space opens up again and the only thing that can quickly fill up that space is air that is sucked in from the surrounding tissue. Think of the disc like an empty ketchup bottle where the inner nucleus pulposus or ketchup is completely finished.

When you squeeze the ketchup bottle together like when you are standing, it flattens out. But when you lie down it expands to its normal shape and sucks in air. Overall, this finding on a CT scan typically suggests that there is excessive movement between the bones and implies that you may require a fusion. 

Yes, normally the intervertebral discs should bulge when a person is moving like bending forward. However, the bulge should quickly correct once the spine is back in normal alignment. When the disc becomes worn out and loses its elastic properties, it can no longer stretch back into position and so it stays as a bulge.

When it bulges out excessively, it can compression the surrounding nerve roots which are traveling just behind it. Normally, a disc bulge is not painful. There are many studies showing that patients with no back symptoms or pain can have disc bulges. In fact, there are many studies that have found disc bulges that compress the surrounding nerves, but the patients have no nerve pain.

The reason that some disc bulges are painful and others are not, seems to be related to whether there is inflammation around that area. Once an inflammatory response is activated, patients tend to have back pain. This is the reason that anti-inflammatory medications like advil or steroid injections work; they help suppress this inflammatory reaction.

A black disc refers to findings on an MRI scan. Normally discs have two separate colors which is an inner white color and an outer black color (more precisely known as a high and low intensity area, respectively). Once a disc becomes work out and degenerates, it loses its normal appearance on an MRI scan so that the inner layer is no longer white, but appears as a black disc.

The inner layer (ie. Nucleus pulposus) is normally white because it’s filled with proteins that attract water and is basically over 90% water). As the inner layer ages and gets worn out, it loses its proteins and therefore its ability to attract water. As a result, it no longer lights up as a high intensity or ‘white’ area, and becomes similar in color to the surrounding outer layer (ie. Annulus fibrosus). This gives the appearance of a back disc.

Unfortunately, you cannot prevent a disc from bulging. This is not only because it is normal for a disc to bulge to some degree, but also the reason for the bulging is due to factors beyond your control including aging. As you get older, your soft tissues, including the disc, lose its elasticity or its ability to spring back when stretched.

This is why when you get older your skin sags or your wrinkles show. Likewise, the intervertebral disc does not stretch back into normal shape and position when it is loaded with forces. Of course, keeping yourself well hydrated can help maintain the fluid within a disc and hopefully its ability to spring back into position.

Likewise, there are many activities that excessively load the disc and put pressure on the disc to bulge or herniation. Bending over and lifting excessively heavy objects, or driving on a very bumpy road, all leads to excessive downward pressures on the spine and discs so that the only way to disperse those forces is for the discs to bulge or herniation.

This is why truck drivers are at increased risk for developing neck and lower back disc herniations; they are constantly on the road and their spines are constantly being axially loaded as they bounce up and down on the road. 

The majority of bulging discs do not need any treatment. However when a disc bulge becomes excessively painful or starts to compress the surrounding nerve roots, treatment options are necessary. This can range from simple things like physical therapy to more interventional options like injections or surgery.

Unfortunately, no scientific studies have shown that any specific medications can prevent or treat disc bulges. Of course, that does not mean that healthy nutrition and maintained hydration can’t help, but that we just don’t have the evidence to show that it actually has a strong impact.

Of course,  a variety of medications have been shown to be effective for managing back pain and your physician can discuss the pros and cons of the different medications. Other conservative options for treating a bulging or herniated disc include physical rehabilitation or manipulation, as well as support braces or orthoses.

Physiotherapy can help strengthen the surrounding spine muscles and abdominal muscles known as the ‘core’ muscles. Other than the disc, ligaments and joints which are the ‘primary’ stabilizers of the spine, the surrounding muscles can be thought of as ‘secondary’ stabilizers.

Physical therapy helps by strengthening your secondary stabilizers so that there is less stress and strain on the primary stabilizers. Likewise, manipulation therapy including chiropractic therapy, acupuncture, and massage therapy have all been shown to help symptoms of back pain to some degree.

Other options include traction and support braces. Traction works by stretching out the disc but its effects are only temporary. Nevertheless, it may provide reasonably good relief for several hours. Likewise, support braces or orthoses (eg. lumbar support orthosis or back-brace), can help alleviate back pain by providing secondary stabilization, similar to your core muscles. 

There are multiple interventional options available for treatment of disc herniation. Spinal injections can help when nerve roots are compressed and there is significant inflammation in the surrounding area. Unfortunately, there is limited evidence that disc injections provide any significant long term relief.

Other options include surgery and there is a wide variety of treatment methods which all depend on the precise problem with the disc. For example, if the problem is only a disc herniation, then a discectomy procedure can be done to remove the disc (often called a microdiscectomy because we use microscopic tools to remove the disc).

On the other hand, when the disc is very worn out, we can either fusion the bones together and put a bone graft to fill the space where the disc would normally have been, or we can replace the disc with an artificial disc replacement.

The treatment options really depend on several factors, including the quality of the disc, the symptoms you are complaining of, and the preferences of your surgeon.