What is Degenerative Disc Disease (DDD)?
|
Even if I were to discount the last 10 years in which I have worked as a spinal specialist, I have lost count of the sheer number of people that have turned up to my clinic in a blind panic after they have been told they have, or are likely to have, Degenerative Disc Disease (DDD). In reality, this is a very misunderstood term and after I have picked them up, dusted them down and actually explained their scan results, or put in to perspective Dr Google's diagnosis, we can then crack on with getting them better. So what is this 'disease' that worries so many of my clients? |
Degenerative Disc Disease - The Truth?
Degenerative Disc Disease (DDD) is a phrase that originated many decades ago to describe what is more commonly known as 'ageing' of the intervertebral disc. Despite being very common in adults, it is very difficult to speculate the exact occurrence rate due to broad variations in published research. What we do know is that the older we get, the more chance we have of developing it, HOWEVER, advancements in research are now suggesting that up to three quarters can actually be attributed to genetic factors.
It is very important to understand that despite the name, this is not really a disease, in the truest sense. In fact many professionals believe that the stigma associated with phrases like 'disease', can, in their own right, be detrimental to some people. This is especially true in those of us with personalty types that are more prone to being anxious and having an over active brains. In my experience the latter group are often bright people in academia, research, developmental and analytical job roles. I personally think that having an active mind that is effective at thinking laterally, in ways that others do not is what enables these people to do the jobs they do, but invariably, this can also mean that they are more prone to think about health related issues in different ways as well - perhaps the common headache turns into brain tumour!
Hopefully the following will help to dispel some of the misnomers and incorrect beliefs that we commonly hear regarding this.
For the sake of this article we will concentrate of the lumbar spine, that is the lower part of your back. You will then be able to apply the principles of this throughout the spine to fit broadly you own presentation or condition.
It is very important to understand that despite the name, this is not really a disease, in the truest sense. In fact many professionals believe that the stigma associated with phrases like 'disease', can, in their own right, be detrimental to some people. This is especially true in those of us with personalty types that are more prone to being anxious and having an over active brains. In my experience the latter group are often bright people in academia, research, developmental and analytical job roles. I personally think that having an active mind that is effective at thinking laterally, in ways that others do not is what enables these people to do the jobs they do, but invariably, this can also mean that they are more prone to think about health related issues in different ways as well - perhaps the common headache turns into brain tumour!
Hopefully the following will help to dispel some of the misnomers and incorrect beliefs that we commonly hear regarding this.
For the sake of this article we will concentrate of the lumbar spine, that is the lower part of your back. You will then be able to apply the principles of this throughout the spine to fit broadly you own presentation or condition.
Intervertebral Disc Anatomy?
Intervertebral discs consist of two main sections, an outer annulus and an inner nucleus pulposus. They are connected to the surrounding vertebrae by 2 end plates, one on the top and one on the bottom. They are located between the vertebrae, in our spines, separating the large bony areas at the front. - see below.
The lumbar vertebra, end plates, nucleus pulposus and annulus. For reference, the tummy is to the left-front side and the back is towards to the upper right.
The Annulus Fibrosus
This outer structure consists of between 15 to 20 sheets of fibrocartilage (Type 1 & Type 2 collagen) that we call lamella. These are a type of strong, inelastic, protein similar to those that make up your ligaments. In cross section they look very similar to a sheet of plywood, having a unique design where by each layer runs at 120 degrees when compared to its neighbour. This type of structure has a naturally high resistance to tension (stretching force) however a low resistance to compression (squashing). Between these layers is an elastic coating which helps the overall disc structure adapt to different loads and forces and reduce the chance of injury and/or failure.
The Nucleus Pulposus
This viscous (thick) liquid, similar to the elastic coating in the annulus described above, is best thought of as like the soft centre of a jam doughnut. Made up from a mixture of water (70%), prostaglandin (28%) and collagen (2%), the nucleus helps to maintain the outward pressure needed to support the compression loading through the disc structure.
This dual system between both the annuls and nucleus is essential because like a bicycle tyre, the disc will only operate at its best when it is healthy and 'fully inflated'.
This dual system between both the annuls and nucleus is essential because like a bicycle tyre, the disc will only operate at its best when it is healthy and 'fully inflated'.
The Bony End Plates
There are two cartilaginous end plates which sit on the top and bottom of the individual discs. They are joined at the inner edge of the annulus, to the disc, and then merge to the bony surfaces of the vertebra, above and below. They essentially anchor the disc and keep the annulus and nucleus contents separate from the vertebral body.
How Does The Intervertebral Disc Work?
The best way to think of the disc is to imagine its role within the spine as a 'spacer' between the adjacent vertebrae, as well as a 'shock absorber'. The disc undergoes a constant repair/destruct cycle as it absorbs the forces we put through it, a process which is sustained by sufficient delivery in and out of the disc, of nutrients and metabolic waste.
In childhood, our discs have a direct blood supply enabling this exchange mechanism to occur effectively. At around the age of 18-20 however we loose this direct blood supply and the exchange process is thought to take place instead through very small channels in the end plates. Although this system remains effective in the most, it does appear to be more susceptible to failure with some theorising that this is a key component in the onset of DDD. This may be why degeneration appears to be far more common after adolescence (adulthood), increasing in commonality with age.
When the balance of this system falters, the outward pressure of the disc begins to reduce (like a balloon deflating very slowly) and the annulus begins to loose its normal resistive properties, especially to its already weakest characteristic, compression, as well as torsional (twisting) forces. This can lead to acute, or chronic trauma, such as minor delamination, or splitting, of the annular layers which ultimately alter the discs structural properties further (think of how that plywood layers can slightly separate if you leave them in the rain, or wet - in a minor way). In some cases, most notably if these changes occur at the very back of the disc, where the sinuvertebral nerves supply the annulus, it may have the potential to give you pain as well.
In childhood, our discs have a direct blood supply enabling this exchange mechanism to occur effectively. At around the age of 18-20 however we loose this direct blood supply and the exchange process is thought to take place instead through very small channels in the end plates. Although this system remains effective in the most, it does appear to be more susceptible to failure with some theorising that this is a key component in the onset of DDD. This may be why degeneration appears to be far more common after adolescence (adulthood), increasing in commonality with age.
When the balance of this system falters, the outward pressure of the disc begins to reduce (like a balloon deflating very slowly) and the annulus begins to loose its normal resistive properties, especially to its already weakest characteristic, compression, as well as torsional (twisting) forces. This can lead to acute, or chronic trauma, such as minor delamination, or splitting, of the annular layers which ultimately alter the discs structural properties further (think of how that plywood layers can slightly separate if you leave them in the rain, or wet - in a minor way). In some cases, most notably if these changes occur at the very back of the disc, where the sinuvertebral nerves supply the annulus, it may have the potential to give you pain as well.
IMPORTANT
It is vitals important to understand that disc degeneration in its own right is considered NORMAL, and having these changes DOES NOT automatically mean you will get pain. Degeneration only becomes a clinical issue when the disc, or other structures, have been altered in a way that gives rise to pain by some mechanism. I often describe to my clients that changes in the disc can often overload other structures as well, such as the soft tissue or joints, and in fact in can be these structures that eventually give rise to the pain, not the disc itself. In reality, because we do not have a pain scanner yet, I can not always be sure of the exact pain generator so this description I use, is based solely upon my experience of patient pain descriptions as well as overall clinical presentations.
As a physio I explain this concept A LOT (and I mean a lot!) to patients who come to me with significant worries after being given a scan report that has umpteen big words related to degeneration written on it. More often than not these are simply signs that you are no longer 21 years of age (sorry to break the news to you) but do not mean you have a spine that is crumbling, breaking away, fragile, about to snap or is likely to confine you to a wheelchair if your so much as lift a feather. In all likelihood the report will probably be describing, in medical lingo, how boringly normal you are for your age - you just did not know it before.
There is significant debate in the spinal research world, in which I am an active participant, regarding how many MRI scans we should really be undertaking. Aside from the obvious financial implications to the health service there is a definite fear amongst some that poor, or irresponsible, 'translation' of reports in to leyman terms for patients, can actually increase the chance of them developing unnecessary chronic conditions simply from 'sewing the seed' of fear or doubt. I am sure that most of you will agree that the power of suggestion, especially in an already worried or anxious person, can lead to all sorts of inappropriate and ultimately untrue scenarios/situations which can cause very negative, and quite destructive panic responses (we call this catastrophisation).
Personally I do feel we need to scan patients with worrisome symptoms, or those who are not following accepted healing expectations, but the professionals delivering the results should know what they are talking about and understand the implications of miscommunication those results to the lay person.
There are currently research projects developing, and testing, very fast MRI studies that take fewer 'visual slices' to ensure that there are no significant anatomical anomalies. This may then be the happy half way between limited resources and patient safety/reassurance, as long as the results are delivered properly.
There is significant debate in the spinal research world, in which I am an active participant, regarding how many MRI scans we should really be undertaking. Aside from the obvious financial implications to the health service there is a definite fear amongst some that poor, or irresponsible, 'translation' of reports in to leyman terms for patients, can actually increase the chance of them developing unnecessary chronic conditions simply from 'sewing the seed' of fear or doubt. I am sure that most of you will agree that the power of suggestion, especially in an already worried or anxious person, can lead to all sorts of inappropriate and ultimately untrue scenarios/situations which can cause very negative, and quite destructive panic responses (we call this catastrophisation).
Personally I do feel we need to scan patients with worrisome symptoms, or those who are not following accepted healing expectations, but the professionals delivering the results should know what they are talking about and understand the implications of miscommunication those results to the lay person.
There are currently research projects developing, and testing, very fast MRI studies that take fewer 'visual slices' to ensure that there are no significant anatomical anomalies. This may then be the happy half way between limited resources and patient safety/reassurance, as long as the results are delivered properly.
