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Conditions
Slipped Disc |
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| The human spine is made up of individual vertebrae, or
units of bone, that are stacked on top of each other. Intervertebral discs sit between
these units of bone, acting as shock absorbers – they are made up of a hard, outer
layer (the annulus fibrosis) and a soft, inner core (the nucleus pulposus): |
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| If the spine becomes compressed for any reason, the
pressure on one (or more) of the discs is increased. If the pressure becomes too great,
the disc will start to bulge; eventually, it may even burst – if this happens, the
outer layer will rupture and the inner core spurts out (a condition referred to as a
complete, herniated disc): |
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The pain associated with either condition is usually
severe. The outer layer of the disc is well supplied with nerves and, as a result, pain is
often caused (without nerve root compression) by mechanical distension, or stretching, of
the outer wall. In addition to this, a bulging or herniated disc will often exert pressure
on the nerves that branch off the spinal column, causing pain. Herniated discs are usually
more painful, because the ruptured, inner core spills out into the surrounding area,
causing more problems.
At this stage, it is important to be clear about terminology. The terms bulging, and
herniated, disc are clinical terms that accurately describe certain aspects of disc
pathology. Slipped disc is a generic, lay term that may refer to either of the two
previous conditions (please note, however, that the term ‘slipped’ is incorrect
– this gives the impression that the entire disc slips, or moves sideways – this
does not happen).
Finally, please note that the term prolapsed disc is often used by the medical
profession to mean different things. When some people refer to a prolapsed disc, they mean
bulging; others use the term to refer to a complete herniation (where the outer layer
splits and the inner core is expelled). It isn’t surprising that some patients get
confused! |
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Why does this happen?
The discs that separate the vertebrae are designed to be flexible – they need to
accommodate the spine when it moves in several different directions. For example, when we
bend over (either backwards or forwards) the discs are squashed at one end, and enlarged
at the other: |
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The discs are uniquely equipped to handle this movement
– the inner core is soft, and is designed to move within the disc, transferring from
one side to the other (and back) as the spine moves in various directions.
So, the discs are obviously designed to handle compression – the question is, how
much? If too much pressure is applied, both the inner and outer layers will deform,
without returning to the centre of the disc; that is, the disc starts to bulge. If the
pressure isn’t reduced (or, worse still, if it’s increased) the disc will
continue to bulge; over time, the structure weakens and, eventually, the outer layer will
split – either partially (in which case the inner core remains trapped) or
completely, in which case a hernia forms.
In theory, a herniated disc can occur anywhere in the spine. However, in practice, the
vast majority of all hernias (c. 95%) occur in the lumbar spine (the lower back), where
the discs are subject to the highest level of compression.
The remaining hernias tend to form in the cervical spine (the neck), despite the fact that
the intervertebral discs in this region are subject to less compression than discs
in the thoracic spine (mid-upper back) – this is because the range of movement in the
neck is far greater than in the mid-to-upper back and, as a result, the discs in the
cervical spine are subject to far more wear-and-tear.
At a basic, anatomical level, the compression that leads to a herniated disc is caused by
compression of the spine; in turn, this is caused, by compression of the facet joints that
lock the vertebrae together. To learn more about the anatomy of the spine (and the
underlying causes of back pain), please visit our section on the Anatomy of Back Pain. |
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How is it diagnosed?
The symptoms can vary, depending on the severity and location of the damage. If a minor
bulge is present, the pain is often localised to the back; however, if the spinal nerve
roots are compressed (by a significant bulge or herniation) the symptoms are often local and
referred – that is, they are experienced in other areas of the body (into which
the nerves extend), as well as the back.
For example, if a lumbar disc is affected, the pain (and other symptoms) will often
radiate into the buttocks, thighs and legs – a condition referred to as sciatica. However, if the damage occurs in the
cervical spine, the pain will usually extend into the neck, shoulders and arms; radiating
chest pain is caused by a damaged, thoracic disc.
The symptoms also include problems with motor function; that is, in addition to producing
pain in response to a harmful event (thereby alerting the brain to the problem), the
nerves also control the muscles that allow us to move, and the organs that allow us to
function normally. If the nerves are compressed, the symptoms can also include muscle
paralysis (whether partial or complete) and organ dysfunction.
Hence, if the rules of both local and referred symptoms (including pain, and muscle and
organ dysfunction) are clearly understood, the patient can be physically examined to
produce a very accurate diagnosis. Some practitioners prefer to use MRI and CT scans to
assist their diagnosis, but these are of limited value in mapping symptoms to pathology. |
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What are the consequences for back pain?
As mentioned previously, a compromised disc (whether bulging or herniated) is usually very
painful. The symptoms also extend into other parts of the body and can be very severe and
troubling for patients. For example if the S1 nerve root (which exits the spine between
the S1 and S2 vertebrae) is compressed, the pain will be experienced in the lower back,
possibly radiating into the buttocks. In addition to this, numbness and pain may be felt
on in the foot, and partial or complete paralysis of the ankle (foot drop) may be
experienced. On the other hand, damage to the nerve roots from S2-S4 may affect the
bladder, bowel, or sexual organs.
Note: Although the sacrum (a fused bone at the base of the lumbar spine, comprising
five vertebrae: S1-S5) doesn’t contain any discs, it is still possible for a
herniated lumbar disc to compress the sacral nerves – despite the fact that
the sacral nerves exit the spinal column via holes in the sacrum, they actually run through
the lumbar spine before doing so (in a structure known as the cauda equina). As a result,
the sacral nerves are, somewhat curiously, susceptible to a bulging or herniated disc. |
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What are the risk factors?
We’ve already seen that compression of the spine can lead to either a bulging, or
herniated disc; the primary risk factors that lead to compression are:
- Ageing
- Bad posture
- Hereditary conditions
- Injury
- Obesity
For example, if a patient is carrying excess weight, this translates into additional
compression of the spine. A hereditary condition, like short leg syndrome (where the
difference between legs is > 5mm), may lead to biomechanical problems that, in turn,
lead to compression.
Ageing is a risk factor in virtually all conditions, but it plays a slightly different
role in spinal disc pathology. For example, most people who experience a herniated disc
are aged between 30 and 40 – the condition is less common in older people.
This is because, as the intervertebral discs grow older, they become harder and less
flexible as they lose water – although typically referred to as degeneration (which
can lead to its own problems), it makes the inner core harder, and less likely to distort.
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Can it be treated?
Patients with a bulging, or herniated, disc are usually offered a range of conservative
treatments to begin with. These may include physical therapy; osteopathy or chiropractic;
and a range of pain killing, anti-inflammatory drugs
(either taken orally, or injected).
At best, these treatments will help your symptoms for a short period of time. If the
condition fails to improve on its own, you may be referred to a surgeon, for an operation
called a discectomy.
Note: Our opinions on spinal surgery
are well documented in this website – we strongly advise all of our patients not
to undergo spinal surgery. Instead, we believe the correct approach is to decompress, or
mobilise, the spine using non invasive techniques. For example, a bulging, or herniated
disc can be successfully treated by decompressing the spine, but this should be
done mechanically (using carefully applied pressure and/or distraction), and not
surgically.
We believe that orthopaedic medicine is
the most appropriate form of treatment – the backrack™ will replicate most of the methods used by a
practitioner, but, for more serious conditions, you may wish to visit our Spine Clinic in London.
For more details on the range of treatments available, please visit our section on Treatment. |
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