A comprehensive guide to understanding spinal disc injuries and how to treat them
Our spine is a remarkable structure, comprised of individual vertebrae separated by intervertebral discs (IVDs) that act as cushions. These discs consist of an internal nucleus pulposus, and an outer dense collagenous rim known as the annulus fibrosis.
This may sound complicated, but disc injuries are very common.
Below, we’ll delve into the intricacies of IVD injuries, exploring when they occur, the mechanisms at play, and how they manifest in pain.
Image 1: Here is a side-on view (left) and birds-eye view (right) of an intervertebral disc (IVD), situated between two adjacent vertebrae. Weight bearing through our spine is 80% through the vertebral bodies and discs, and 20% through the articulations (facet joints), forming the other half of our spinal column. In this image, the nucleus pulposus has a different appearance to the annulus fibrosus. The nucleus has more fluid content, making it able to resist compression, whereas the annulus has several layers of collagen making it able to resist torsion, shearing and stretch. The annulus is also reparable if it becomes damaged.
Why does a disc injury occur?
Acute disc injuries often result from a mechanical overload or repetitive loading over a short time frame.
The common mechanism involves combined end-range flexion and rotation of the spine, such as bending forward while twisting.
Image 2: This image demonstrates what happens between two vertebrae when we flex our spine. The fluid nature of the nucleus results in displacement towards the rear of the spine when we compress the front end. With most daily movements the annulus can withstand this force. Though you can see how this might result in damage if it is either excessive or repetitive.
What happens to your spine when you encounter a disc injury?
The initial stage of an acute disc injury involves damage to the outer fibrous rim, leading to an annular tear.
This weakening of the tissue may cause displacement of the internal nucleus pulposus, resulting in a disc bulge or herniation.
Annular tears, even without bulging, induce pain due to the inflammatory response and possible nerve irritation.
Image 3: This is a simplistic representation of damage to the annulus leading to a disc herniation. The key takeaway from this image is that there are several layers off collagen making up the annulus, and that when small damage occurs (as on the left) our body will trigger an inflammatory response resulting in healing.
The pain presentation of disc injuries
Like any connective tissue injury (such as a ligament sprain), an inflammatory process will occur.
Though this is a natural and appropriate cellular response to commence a healing process, it can be quite painful, mostly because this injured tissue will continue to undergo mechanical strain with normal daily movement.
Close to the IVD are a pair of nerves that exit the spinal canal (nerve roots), and the presence of inflammation nearby may cause these nerves to generate a pain signal along their path (like sciatica). This is known as neuropathic pain, or nerve pain.
A significant annular tear can cause a disc to bulge or herniate, leading to both chemical (inflammation) and mechanical (bulging) irritation of the exiting nerve roots.
Image 4: This image shows nerve roots exiting our spine at each level. If you trace where these nerves travel, it makes sense how a disc injury can cause pain in unusual places, due to inflammatory and/or mechanical irritation of these adjacent nerves.
Assessing disc injuries in the clinic
We use various methods to assess and treat IVD-related pain.
Key signs of IVD-related pain include localised pain with spinal flexion, tenderness, muscle spasm and pain aggravation with activities like coughing and sneezing.
Neurodynamic tests - like the 'slump test' and 'straight leg raise test’ - help assess nervous system flexibility and may indicate disc pathology. If either of these are ‘positive’ then the likelihood of a symptomatic disc pathology increases.
If we suspect that the back pain is due to irritation of a nerve root, we will perform a quadrant or Kemp test. This test acts to position the patient's spine in a way that narrows the passageway through which these nerve roots exit the spine at each level.
If a nerve root is involved in a person’s pain, then it is very likely that when we move their spine into an extended and side-flexed position, that they will get a return of (or worsening of) the referred pain into the hip or leg.
The Kemps test is also quite sensitive for facet joint pain, so if there is pain in this position that remains localised to the spine, we suspect their pain is related to the spinal joints.
In a healthy state, we should be able to move into that position with only a sense of tightness in the back as you would feel with any other stretch.
Why you may not need to worry about your MRI results
A lot of people experience back pain. Sometimes it is chronic (ongoing pain for several months or more), sometimes it is episodic (not too bad most of the time, with short-lived episodes of pain), and for others it may be acute (generally related to an injury of some kind, often a more severe pain, but resolves in days to weeks).
If you experience an acute episode, and the assessment above points towards a disc herniation, then the presence of a disc herniation on an MRI would most likely be related to the pain you are experiencing.
The good thing is that there is every chance you will have full recovery if you are diligent with seeking advice and adhering to a rehabilitation plan.
In fact, we have case studies showing reductions of a disc herniation on MRI (see image 5 below) based on patients adhering to advice from their practitioner.
Image 5: Before and after of a disc herniation on an MRI.
If you have chronic or episodic pain, and decide to get an MRI, don’t be surprised if there are disc herniations at one or even multiple levels of the spine.
Importantly, if your clinical assessment does not indicate that you have the symptoms of a disc injury, then these herniations may be quite stable, and unrelated to your pain.
Studies have shown us that in general there is weak correlation between the presence of pathology on MRI and the presence of pain (in that area), for many musculosketal conditions.
Image 6: This image shows us that in a group of asymptomatic people (i.e. no pain), that multiple ‘pathologies’ were evident on radiological imaging. As practitioners this doesn’t deter us from ordering imaging when we feel it is necessary, however it does mean we need to be able to correlate radiology results with clinical presentation. For patients, it means you often don’t need to worry if your scans report seemingly concerning findings, as there are people with similar findings who are pain free.
So, how do we treat disc injuries?
If it is clear from clinical testing, subjective history and radiological imaging that the person’s pain is related to the IVD and/or adjacent nerve root, then we use several different treatment methods together to aid in a person’s full recovery, such as:
Pharmaceutical interventions: these can play a key role in management of severe acute lumbar back pain with or without nerve pain (referred pain). We would work in collaboration with your GP on this.
Manual therapy techniques: which will be chosen after assessing a person’s ability to move into, and remain in, certain positions.
Dry needling and soft-tissue massage: provide a non-threatening first line option to reduce muscle spasm and begin calming the heightened pain state.
Joint mobilisation: applied directly to the symptomatic region or segments of the spine will begin reducing pain signals. The small gliding movements applied into the pain barrier will potentially allow your body to engage active movement without triggering a pain response as readily.
Joint manipulation: is known to have a positive impact on acute spinal pain. This will be applied with caution when an acute disc herniation is suspected.
MET (muscle energy technique): this will involve the patient in some active techniques where the practitioner will apply stretch to a joint or specific muscle and ask the patient to perform a muscle contraction to assist with the effectiveness of the stretch.
Exercise interventions: extension movements and core control exercises are often prescribed. This will likely be the most important ongoing protection against acute spinal pain.
Machine traction: may be used to temporarily decompress the spinal area involved.
Treating a lumbar disc injury is a very nuanced process, depending on a person’s pain presentation and injury history.
Each case needs to be assessed properly in order for a patient to regain mobility and result in a reduction in pain.
It’s critical that patients experiencing disc pain seek the advice of a practitioner to aid in their recovery.
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