As we enter National Pain Week 2020 (27th July – 2nd August), I feel it is very appropriate to address one of the leading causes of pain in Australia: spinal pain – specifically, pain caused by degenerative disc disease.
From my clinical experience of five years, I have noticed an unmistakable trend in the breadth of patients I have treated: the fear surrounding disc degeneration and injury is very real. There also still appears to be both very limited and dated knowledge around this type of musculoskeletal issue. Many patients feel their activities of daily living will be forever changed for the worse, without possibility of recovery.
Let’s shed some light on this common type of musculoskeletal injury of the spine to provide some clarity and hopefully – RELIEVE some potentially unnecessary stress!
ANATOMY OF THE INTERVERTEBRAL DISC
First and foremost, let’s establish a sound understanding of the composition of the discs of the spine. From here, one can understand different presentations of spinal pain of discal origin.
The discs reside between the vertebrae of the spine – in all sections: the cervical (neck), thoracic (midback) and lumbar (lower back) regions (hence, their name ‘intervertebral discs’). The discs act as fibrocartilage shock absorbers. They enable each of the different regions of our spine to absorb forces and act to protect the spine (Moore et al., 2017).
(This is Heinrik’s – one of the skeleton brother’s at Hands On Osteopathy - lumbar spine - the intervertebral discs can be seen in between the vertebrae.The red kidney bean shaped object is the representation of a disc bulge)
Intervertebral discs are comprised of:
- An outer fibrous layer, called the annulus (annulus fibrosus). This layer is composed of multiple concentric layers of collagen fibres that are arranged in a cross-hatched fashion. Each of the layers of the annulus alternates – giving strength to the disc structure for multi-directional movements needed in the spine. These fibres, over times, are prone to ‘wear and tear’ with repetitive loading of the spine. The outer few millimetres of the annulus contain small nerve fibres. These outer fibres are susceptible to rupture over time with forces applied to the spine. This can result in episodes of acute inflammatory lower back pain (physiopedia, 2020)
- In inner core called the nucleus (nucleus pulposus): a gel-like part of the disc structure that provides the larger portion of the strength and force-absorption. It is made mostly up of water, with a small portion of chemicals called proteoglycans (physiopedia, 2020)
- Vertebral endplates are cartilage plates that cover the top and bottom parts of the intervertebral discs. The cartilage endplates are responsible for providing nutrition to the disc by allowing perfusion. They also bind the top and bottom parts of each of the disc to the corresponding vertebrae above and below, respectively. These are the last part of the disc structure to degenerate over time. Endplate degeneration is seen in severe disc degeneration. Poor blood supply is available to the intervertebral discs. The endplates are the predominant location of nutrient and toxin perfusion to and from the discs respectively (physiopedia, 2020).
Two ligaments in particular that span along the length of the spine (from the cervical to the lumbar spine regions) provide support to the intervertebral discs from the front and the back; ensuring they are strongly tethered to the spinal column. It is theorised, to some extent, they also provide additional reinforcement to the front and back of the discs to reduce herniation in these locations.
- The anterior longitudinal ligament runs from the base of the skull to the sacrum, connecting the front portion of the annulus to the front portion of all vertebral bodies.
- The posterior longitudinal ligament is located immediately behind the vertebral bodies of the spine (it attaches to these loosely) and the intervertebral discs (it attaches to these firmly). It ascends to the skull from the sacrum, broadening as it travels upwards (Moore et al., 2017).
DEFINING DISC INJURIES
DDD (Degenerative Disc Disease)
As we age, the different types of forces absorbed by the intervertebral discs (distraction; axial compression; flexion; extension; rotational and side-bending/lateral flexion) produce ‘wear and tear’ of the integrity of the outer annulus fibres. This tends to occur in the cervical and lumbar regions of the spine. These regions have the greater ranges of motion and more is demanded of them.
As discs degenerate from excessive loading, the nucleus material begins to migrate outward through the broken areas of the annulus. The shock absorbing abilities of the disc begin to reduce. Once the nucleus begins to do this, the injury is deemed to be a disc herniation.
A disc protrusion (falling beneath the umbrella term ‘disc herniation’) involves contained nucleus material within ‘fraying’ annular fibres. It is yet to outcrop from the disc.
This very injury on its own can produce discomfort unique to each individual – but can certainly disrupt normal spinal movement in the surrounding area (whether it occurs in the cervical, thoracic or lumbar spinal regions). This can produce multiple episodes of acute spinal pain (with each instance of annular tearing). The body can begin to produce an inflammatory reaction in an attempt to promote healing at the site. This type of injury can also occur traumatically: with sudden, excessive load to an already weakened disc.
With final complete rupture of the annulus, the nucleus can extrude. This is deemed to be a disc extrusion in medical imaging reports.
In this instance, the body reacts to the presence of the internal disc material by producing inflammation to clear it away – however it can occupy space that is needed for surrounding nerves (space that is already taken up by the herniation no less!). This type of disc injury can result in nerve impingement and irritation, giving rise to nerve pain. For this reason, this injury’s reputation precedes itself. In severe cases, nucleus material may break off and escape into the spinal canal (disc sequestration), causing more serious instances of nerve or spinal cord impingement. Surgery is recommended in this instance.
Disc dessication is the most common of all disc injuries – the discs dehydrate over time with age (as they are predominantly comprised of water). Slow death of the cells that maintain the disc produces this effect. The discs begin to flatten out and the annulus can thicken in response to increased load (from the now lack of force absorption) (physiopedia, 2020; Moore et al., 2017).
The body is very capable of healing these different variations of disc degeneration and injury. Subsequent to the inflammatory reaction, reabsorption of herniated disc material can occur as well as ‘scarring’ or fibrosis of the outer layers of the annulus. Rest and rehabilitation are necessary for this.
Osteopaths are very capable of assisting patients on this journey through appropriate lifestyle activity adjustments and prescription of an appropriate rehabilitation programme.
One thing to be cleared up – and it STILL continues to be uttered by patients when visiting Hands On Osteopathy:
“I have a slipped disc”
To this day I do not understand the origin of this description of disc injury.
It makes no sense. In no way anatomically can a disc ‘slip’.
The vertebral endplates (superior and inferior) adhere the discs to the vertebrae above and below, respectively.
This is a highly incorrect term and description.
It is not a good term to be thrown around to simplify the concept of the injury and should cease to be used. It not only paints an incorrect image of the injury, but unnecessarily instils a fear of severe instability into those who have been diagnosed with disc herniation, sequestration or dessication.
If diagnosed with disc degeneration by a medical professional, please do not hesitate to ask this professional (or a qualified manual therapy practitioner) additional questions to broaden your understanding. It is our job. Clear understanding of your diagnosis is an important first step on the road to recovery. Lack of understanding breeds fear and uncertainty. Both of these can produce enough anxiety in a patient that can impede their healing – from a fear to do anything and a fear that the body will somehow fall apart from its “fragility”.
If you know of a friend, relative or co-worker struggling with pain or a lack of understanding of degenerative disc disease, encourage them to seek medical advice from their GP or manual therapist of choice.
Take care everyone.
Lenore Dyson
REFERENCES
Moore, K. L., Dalley, A. F., Agur, A. M. Clinically Oriented Anatomy (8th Ed) Wolters Kluwer (2017)
Intervertebral Disc Anatomy (https://www.physio-pedia.com/Intervertebral_disc) (Accessed 20th July 2020)
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