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Degenerative Disc Disease (DDD)

Written by Chris Heywood
Cons Physiotherapist

In the 23 years of my career, 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

DDD sounds bad - but how bad it is really & how worried should you be?

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​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 most perceived 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 personality types that are more prone to being anxious and having an over analytical brains. 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.

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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 Anulus 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.

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.

It is vitally 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.

When I first started my spinal research role in 2009, one of my primary projects was that of the Genodisc project. This was a 5 year European funded project investigating the part genetics had to play in disc degeneration as well as the possible roles that cell therapies could play in the halting, or even reversal, of this process. As a result of this project, and others, it is now thought that up to 70% of this 'degenerative disc' process can be explained by our genetics, meaning that environmental causes such as jobs, hobbies etc may play much less of a roll than previously thought. This is especially true in the cases of younger patients (sub 30 years) where we would not normally expect to see these 'age related' changes.

It may also explain why we see so many families, through varying generations with similar back pain presentations. As clinicians, we picked up on this a long time ago but it is only in the recent years however that we are beginning to see the advancements in research backing this up. 

As I have alluded to above, the symptoms of DDD are difficult to describe as it is entirely normal to see people with degenerate discs who have no back pain related to them at all. To hit this fact home further it is estimated that approximately 30% of the whole UK population, if scanned, would have clinically significant changes to their spine, however many of these would not have, nor ever did and may in fact may never have, any back pain symptoms at all - weird but true - welcome to my world!

It is thought to be possible to get sharp pain from annular tears, due to the direct nerve supply at the back of the disc, but more often that not it is pain arising from other structures that may be over loaded or inflamed (such as facet joints), compressed (such as nerves), or mechanically irritated (such as spinal instability), due to the reduced health of the disc.  The only way to clearly identify the presence, and level of DDD is by MRI, but as this does not tell you where, or if, any pain is arising from the disc, there does have to be a good clinical reason for ordering the scans in the first place. In many cases it is impossible to be anatomically definitive in terms of the primary pain generator and as we treat a lot of back pain in similar ways, it may not alter your treatment effectiveness, as long as you are in the hands of a good specialist or expert therapist.
 
At the end of the day, in the absence of any indicators of serious pathology or injury (Red Flags) it is widely acknowledged, as well a supported by a plethora of evidence, that exercise is the best way to combat most forms of back pain. What we don't know is which exercise is the best and truth be known, there are so many variables that could influence back pain, from the way our brains work differently (processing and controlling pain), to subtle differences in what is actually the root cause(s) of the problem, that we may never know.

That is why we are proud to employ some of the best practitioners in the region, at Team Rehab uk, across both our clinics in Corby and Moulton, Northants, so that you can be sure you will get the best assessment and subsequent treatment (if necessary) to enable you to either get better, or self manage you condition, to the best of your ability.

Most people with symptom inducing DDD can be effectively helped by physiotherapy. This may be as simple as facilitating the recovery of a flare up or as complex as planning, and developing, an individualised muscle strengthening plan to help relive some of the pressure from your spine (think of building the correct muscle around your spine as erecting some decent scaffold to give it a helping hand). Where land physiotherapy does not work we can also offer hydrotherapy where you can be exercised in a very different way but with the same aim of building muscle strength and stamina. Manual therapy (joint mobilisation/manipulation), soft tissue work and taping (as a brief example) can also be used to help relieve local tension and adverse stresses on the spine

We are proud to employ some of the best practitioners in the region, at Team Rehab uk, across both our clinics in Corby and Moulton, Northants, so that you can be sure you will get the best assessment and subsequent treatment (if necessary) to enable you to either get better, or self manage you condition, to the best of your ability. Why not visit our review page so that you can get a snap shot of how we have already helped thousands of patients across the region.

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