Most people know somebody who has ‘slipped a disc’ but what does this really mean?
Often when patients present at the clinic with back pain, the first thing they worry about is their discs. There is a lot of scaremongering where discs are concerned and as soon as they are mentioned as a diagnosis many patients start to worry that they will be in pain forever and are ultimately heading for surgery. It is important to remember that like most problems, disc injuries can vary hugely in their severity and therefore in the recovery pattern.
What is a disc exactly?
The intervertebral discs are the structures in-between adjacent vertebrae in the spine. They are made up of an outer fibrous ring (the annulus fibrosus) and an inner gel like centre (the nucleus pulposus). The nucleus pulposus of the disc acts as a shock absorber, distributing pressure evenly in all directions and preventing a concentration of pressure on an area of bone.
Acute Disc Pathology-the classic ‘slipped disc’ presentation
The most colloquial description of disc pathology is that of the ‘slipped disc’, also known as a herniated or prolapsed disc. In this scenario the gel like nucleus pulposus is forced against a weakness in the annulus fibrosus. The disc doesn’t actually ‘slip’ but it may be pushed against the nerve roots which exit the spine at that level. The most common disc to be affected is the L5/S1-the lowest lumbar disc, with the L4/5 just above it being the second most common.
When the disc physically compresses the nerve root causing leg pain it is known as a lumbar radiculopathy and commonly referred to as sciatica. Some patients even find that leg pain rather than back pain is their only symptom of a prolapsed disc.
The disk doesn’t have to actually touch the nerve root to cause leg pain. The same symptoms can be produced by chemicals which leak out of a compressed disk causing irritation or inflammation of the nerve root.
Causes of disc injuries
Disc injuries are most common in those aged 30-50. Whilst lifting heavy loads, torsional stresses and motor vehicle driving have been identified as environmental risk factors, genetic links have also been found. Unfortunately it seems bad backs do run in families!
A disc injury can be traumatic, usually from a sudden forced flexion movement, tearing fibres of the annulus fibrosus, allowing the nucleus of the disc to herniate posteriorly (backwards). Examples of this sort of injury include bending to pick up a heavy object or being pushed from behind into a bent position during sport or in a car accident.
A disc injury can also arise from relatively little provocation. Cumulative pressure over time, perhaps from repetitive flexion tasks or prolonged poor sitting posture may lead to dehydration of the disc so that it becomes less flexible and more prone to tears. A typical scenario might be someone in a sedentary job, whose back locks ups suddenly in spasm whilst bending to put their shoes on in the morning.
Degenerative disc disease
As we get older the nucleus pulposus of the disc begins to dehydrate and its’ ability to absorb shock is reduced. These changes are referred to as degenerative disc disease. They are a normal part of the aging process. Whilst it would not be unusual for somebody in their 50s or 60s to have signs of degenerative disc disease on an MRI scan, in younger patients it can be considered a more significant finding and may be related to lifestyle or genetic factors. Loss of disc height and shock absorbance also means that the joints in the spine are loaded more. These facet joints can start to show degenerative changes and become another source of pain.
Common symptoms associated with a herniated disc include:
• Pain referring down one leg
• Pain coughing and sneezing
• Pain with bending
• Difficulty standing up straight or feeling as if you are shifted to one side.
• Pins and needles or numbness in the leg
You might experience some or all of these symptoms. However if a disc injury is suspected it is also important to be aware of certain ‘red flag’ symptoms.
• Recent onset of bladder dysfunction
• Recent onset of faecal incontinence
• Pins and needles between the legs
• Progressive weakness of both legs
These symptoms are rare but very important to rule out as they can be signs of a cauda equina compression. In very severe cases a disc bulge can compress the cauda equina, which is the very end of the spinal cord where it exits the vertebral column. If there is any question of this being compressed you will be referred for urgent investigation and surgery will likely be required to prevent permanent damage.
If you see your GP with the above symptoms (red flags aside) you will usually be advised to take non steroidal anti-inflammatories and paracetamol. Often over the counter medication is sufficient to ease the pain.
If your back is ‘locked up’ with muscle spasm, you may be prescribed an anti-spasmodic drug to help your muscles relax so that you can move again.
If your nerve symptoms in the leg are very persistent over time you may be advised to take a mild anti-depressant or gabapentin which have an effect on modifying neuropathic pain.
Your physiotherapist will assess you thoroughly before diagnosing a disc problem. If there are no red flags, then it is not usually necessary to confirm the diagnosis with an MRI scan straight away. A combination of the following treatments may be used to ease your pain and help you to start moving again:
• Manual therapy including massage
• Gentle mobility exercises in pain free directions
• Supportive taping or Kinesiotaping
• Posture advice
• Early core stability exercises
• Modified Pilates exercises
With a combination of analgesia and physiotherapy, the majority of patients will make progress in terms of their pain and movement. Progressive spinal stability exercises aim to strengthen the muscles supporting the spine to reduce loading on the discs allowing healing to take place. Whilst it is very rare to perform a follow up MRI scan on a patient who is symptom free, it is assumed that the disc bulge resolves itself in many cases with this treatment approach.
If your pain is very severe and you make slow progress you may be recommended to a specialist for further investigation. An MRI scan can confirm the diagnosis of a herniated disc. However, as discussed above, sometimes there can be radicular pain without the disc touching the nerve root due to the chemicals and inflammatory cells involved. There will often be a loss of disc height and the disc will look dehydrated.
If you have severe pain, which has not settled with physiotherapy your specialist may offer you an epidural injection. Anaesthetic and local steroid are injected into the epidural space between the outer covering of the spinal cord (dura) and the vertebra at the level of the disc lesion. Whilst this procedure does not shrink the disk bulge itself it can reduce pain by reducing inflammation in the area. This may allow you to move more freely and continue physiotherapy, whilst the disc bulge gradually resolves itself.
Discectomy-the dreaded surgery!
Red flags aside, it is important to realise that surgery is not the first line of treatment for disc injuries. In fact some statistics indicate that only 10% of patients presenting with a disc lesion have significant pain 6 weeks later to consider surgery as an option. However if you do get to this stage, reassuringly both standard discectomy (removing the whole disc) and microscopic discectomy (removing only the bulge) have been found to have positive outcomes on pain.
Whilst in can be scary to be diagnosed with a herniated disc, don’t forget that the majority of these injuries resolve without any surgical intervention and with a return to full function. To prevent re-occurrence you should try to address any risk factors in your environment and lifestyle where possible. Continuing a regular programme of spinal stability exercises after a disc injury is also thought to be of particular importance.
By Nikki Richards MPHTY(Sports) BSc(Hons)Physio MCSP
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