This blog post is to discuss bulged discs and the misconceptions surrounding them.
It is an article of faith among many mainstream experts that the discs present between our spines can slip out of place and hence they casually call the condition a “slip disc” which causes severe pain and requires avoidance of certain movements like the spinal flexion aka forward bending.
What do we picture when we think of our spine? What is its function? Is it really as fragile as we think? are the words ‘slip disc’ enough to deter our belief in the robustness of our spine?
Let us start with some basic spine anatomy
Our spine is made of 33 vertebrae aka the small bones that form our spine. Each vertebra is connected to the other by an intervertebral disc, which makes up about 20%-30% of the vertebral column’s length and is made up mostly of water.
The function of the IV (Intervertebral) disc is to separate two vertebras, thereby providing the space for increased range through which the spine can move and transmit the load from one vertebra to the next. Seems pretty important!
Moreover, important structures in our body like the brain and heart have their own cage of protection around them, the skull and the ribcage respectively, likewise; our spine (vertebral column) has a very important structure, the spinal cord passing through it. Through this, we can conceptually understand the need for the robustness of our spine.
Now! do we really need to actively protect something that is made for protection? Let’s not forget the network of muscles and ligaments around our spines, and we all know the functional description all these structures fit best is MOVEMENT!
If you are still not convinced about why movement restriction is not ideal for your spine,
it’s important to remember that the IV discs do not receive primary blood supply from any major arterial branches but instead via DIFFUSION for most parts and convection for the rest. which makes movement necessary for the health of your spine. (An animal study in the spinal journal 2015 suggests that low rate loading (slower cyclical loading) enhances the nutritional supply to the disc nucleus and accelerates the uptake and removal of molecules in the disc. Although inconclusive, further research into this can explain the role of loading on disc nutrition, health, and degenerative changes.)
The question that arises here is where do the fear of spinal movement and “slipping” of our discs come from and can disc slip?
No surprises here, the intervertebral disc cannot slip ever since they are firmly attached to your vertebrae by the endplate but it can herniate which is the displacement of disc material ( the term herniate includes all classification like protrusion/bulge, extrusion, sequestration), which may or may not be painful and not even be the cause of your low back pain.
Does a specific posture or movement cause herniation of the disc?
No.
Disc herniation can occur because of multitudes of factors and in many individuals it is asymptomatic.
Numerous studies show that many types of structural abnormalities are poor predictors of pain.
In a 1994 study, MRIs were performed on subjects who did not have back pain, Fifty-two percent of the subjects had at least one bulging disc or other MRI abnormality for which surgery is sometimes recommended.
Given these findings, the authors stated that: “the discovery by MRI of bulges or protrusions in people with low back pain may frequently be coincidental.” In a similar study, MRIs on individuals who had never suffered from low back pain revealed that one-third had a spinal abnormality on their MRI and 20% under the age of 60 had a herniated disc.
In a systematic review, Brinjkji et al (2015), conducted using a study of 3110 individuals from 1946 to 2014, concluded that about 30% of 20-year-olds, 40% of 30-year-olds, 50% of 40-year-olds, 60% of 50-year-olds, 69% of 70-year-olds and 77% of 70-year-olds have a disc bulge with no pain.
The authors of the study summarize:
“Imaging evidence of degenerative spine disease is common in asymptomatic individuals and increases with age. These findings suggest that many imaging-based degenerative features may be part of normal aging and unassociated with low back pain, especially when incidentally seen. These imaging findings must be interpreted in the context of the patient’s clinical condition.”
It would be wrong to say that herniations never cause pain, but the presence of herniation without any pain is a common scenario as seen in the studies above, hence it can be concluded that they are not always the cause of low back pain and it is possible to have no pain and difficulty in the movement even in the presence of disc bulge as seen on imaging.
Moreover, it is seen in a study, that the prevalence of symptomatic IVD herniations in low back pain is only 1-3%.
It is possible to manage the pain caused by herniated discs and lead a normal, healthy life irrespective of the changes seen on your imaging.
In fact, movement is great for our spines, in a 2017 study, it is seen that running or fast walking strengthens the intervertebral disc by increasing IVD hydration, and glycosaminoglycan content and causing its hypertrophy which may well be an adaptation to habitual loading in runners.
Similar to hypertrophic responses seen in muscle due to resistance training, this suggests that tissue adaptation will occur in the IVD with exercise and it is also seen in a study that physical inactivity in people leads to narrow intervertebral discs as compared to people who are active and is also associated with high-intensity low back pain and disability.
So it would be safe to conclude that physical activity and its many benefits are also great for our discs and spines and needn’t be feared.
Also, the ambiguous nature of low back pain cannot be ignored, Approximately 90% of LBP cases have no identifiable pathoanatomical cause, and are called ‘non-specific LBP’, therefore, herniated discs aren’t the cause of a huge percentage of low back pain.
Coming back to where we started,
Why is it wrong to use the term ‘Slipped disc?”
Simply because it creates an idea that our spines are fragile causing movement avoidance and fear.
What to use instead- bulged/ herniated disc
In Conclusion:
1) Discs are not fragile and cannot slip they only bulge or herniate.
2) You don’t need to fear movement.
3) The presence of an abnormality on an MRI scan does not appear to always be the cause of current low back pain or predict future low back pain.
4)Imaging doesn’t always tell the real story, the presence of a bulge on an MRI does not equate to lifelong pain and disability, if it is the cause of your pain, it is possible to manage the symptoms and lead a pain-free life.
In a future post, I’ll write about how herniated discs can heal!
Disclaimer: In the presence of low back pain all the structures and context must be clinically assessed, this blog is in no way a substitute for a clinical assessment and all must consult a physiotherapist or a physician in such conditions.
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Cover Photo by Karolina Grabowska from Pexels
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