"Cracks in the cement" - what can go wrong with the back

The disc and its problems

Back Pain, Disc Pain and Lumbar Disc Degeneration

The lumbar disc has long been the chief suspect in cases of back pain. The term 'slipped disc' has become a part of every day language. Many of us have heard of people having "a disc put back" by an osteopath or "a disc removed by a surgeon". For years most of the money in back pain research was spent investigating painful discs. One back pain expert speaks of the "dynasty of the disc" - meaning that it has become the king of the castle in our thoughts about lower back pain.

It's wrong to focus too much on lumbar discs and low back disc pain like that. We need a wider view of the big picture and should look at the whole person rather than just that little bit of gristle called the lumbar disc.

Sixty years ago in Boston, two doctors first wrote about a patient with low back and leg pain. Seeing that the soft centre of a lumbar disc had leaked out backwards and pressed on the spinal nerve, they put two and two together and assumed this was the cause of their patients problems. The term slipped disc was coined and the patient got an operation - the first of its kind in the world - and made a good recovery. The two Boston doctors became famous and made their fortune in the process.

When this was published it caused great excitement and soon surgeons all over the USA were trying similar operations.

They operated on:

•  people with leg pain

•  people with back pain

•  back and leg pain and

•  a whole host of other complaints they thought might be related.

Sometimes it worked. Often it didn't!

Surgeons today are usually very careful in deciding who should be offered an operation and no longer work on a "try it and see" basis.

Slipped disc or Lumbar Disc Herniation?

Anyway, back to our story about slipped discs and disc pain (sometimes called discogenic pain). For many years surgeons thought that discs only caused problems when they bulged out at the back and squeezed a nerve. This pattern of lumbar disc bulge pain or lumbar disc herniation is commonly spoken about. This is a nice story and can be found, explained in detail, in many textbooks. Unfortunately it's not true - well, at least, not completely!

What's wrong with the old slipped disc theory?

•  Firstly; it soon became obvious that some people with bulging lumbar discs didn't have any low back pain or leg pain. Strangely many of them had never had pain. Stranger still was the fact that many who did have lower back and leg pain had no evidence of abnormal discs, herniated disc, bulging discs or slipped disc when surgeons looked inside their back.

•  Experiments were tried where scientists tried to make the soft centre bit of the lumbar disc bulge out. They couldn't do it! No matter what they did to these discs no lumbar disc bulging or slipping occurred - not even when they took a sharp knife and tried cutting the lumbar disc almost in half. The liquid centre bit stayed stubbornly where it was.

•  The plot thickened even further when other scientists showed that if you pressed on a normal nerve root in the spine it didn't cause leg pain.

How then, with all this evidence to the contrary did the idea of the bulging disc or the slipped disc retain its popularity. How indeed?

Part of the problem was that the anatomy specialists were still absolutely positive that the lumbar discs had no nerves of their own. They thought that the only way a lower back disc could cause trouble was by irritating something else. But in the 1980's two Australian scientists showed that not only did discs have nerves - they had lots of them. Doctors then started to think that a lumbar disc could cause lower back pain in it's own right without bulging or slipping anywhere.

The last ten years have brought us forward to a new and better understanding and the above puzzles can now be explained. If discs themselves could hurt then of course some people had pain without any signs of bulging or slipping - and if nerve roots don't hurt when squeezed then some lumbar discs can slip without causing pain.

Even then though, some questions remained, and the answers are beginning to come now.

The same Australian scientists who had found nerves in the discs also noticed that the soft centre area of the lumbar disc - called the nucleus pulposus - became dried up and like gristle by the age of about twenty five years. After that age it couldn't slip anywhere unless something happened to make it liquid again. That was why experiments had failed to make it bulge out. The discs tested were healthy and normal.

Meantime other researchers had found that although nerve roots didn't seem to mind being squeezed they were made very irritated by having blood or certain of the bodies chemicals anywhere near them.

Discs degenerate! Lumbar disc related pain or "Discogenic Pain"

Lumbar Discs rely on the bones round about them for feeding and nourishment. They don't get any blood of their own to sustain them. The middle bit of the disc - the bit which is soft when we are young - is really a throw back to the days when we were an embryo. It is made of cells which are very different from our adult body cells.

You have probably heard of people getting kidney or heart transplants and then having problems with 'rejection'. This comes about because their own body thinks of the new kidney as "foreign" and begins to attack the newcomer. Well the same thing can happen to a lumbar disc - or at least to the middle bit of it.

If blood is allowed to get in contact with the middle bit of the disc then a reaction very like the transplant rejection reaction happens. The body takes a strong dislike to its own disc and begins to attack it with chemicals called enzymes and other substances called antibodies. We know that comparatively minor disc injury can trigger this process - a fall on the ice, a strain lifting a weight. The attack process may take several years to work or it may occur very quickly. The end result is the same - a disc with a liquid centre again but this time a liquid full of very corrosive and irritant chemicals.

When this liquid gunk leaks out of the lumbar disc it behaves like toxic waste. If it touches the spinal nerve root it causes a fierce reaction which results in leg pain, pins and needles, numbness and weakness - the very pattern some call sciatica.

We used to think those symptoms were due to simple pressure on the nerve root but now realise that it is a burning irritation caused by the disc chemicals that's at the root of the problem.

But sometimes this reaction happens in the disc without the liquid leaking out. It only gets far enough to reach the small nerves in the outer third of the disc. This causes a painful disc and back pain but not the sharp, shooting leg pain which is so typical of nerve root inflammation.

Scientists now think all of this reaction can sometimes happen without any pain at all. If the nerves are not irritated then the brain will remain blissfully ignorant of the process but the disc still gets damaged.

Whether the inflammation has caused pain at the time or not it always causes softening of the disc. This makes the disc narrower and less able to support the weight of the spine. An X-ray can show this narrowing but not until about six months after the process was triggered. This is why X-rays don't often help sort out the cause of back pain.

If the lumbar disc loses its ability to support weight then the lower back part of the spine doesn't just fall down. Something else takes over the strain and this "something" is the lumbar facet joints. These lower back joints cope quite well at first but begin to struggle as the years go by. Lumbar facet joints show distress by getting stiff and painful and it's this - not the lumbar disc - which hurts. This confusion can sometimes make it difficult to plan a course of treatment.

Page Links for lower back pain pages

Lower back pain
What causes back pain
How the spine nerves work
Facet Joint Pain - Sacroiliac Joint Pain
Back pain, disc pain and disc degeneration
lower back pain and the lumbar facet joints
What is Lower Back Pain
Why is my back sore?
Lower Back Pain Treatment and Referred Pain
First aid treatment measures for a low back pain attack
Manipulation Treatment for Back Pain
Acupuncture treatment for lower back pain
Back Pain Treatment

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