The Confusing World of “Slipped Discs”

In between each of the vertebrae of your spine lies a very strong but flexible structure called the disc. These discs have a strong outer rim of fibrocartilage and a soft gel like centre- they are designed to give your spine flexibility and strength and help act as shock absorbers. Discs are frequently implicated as the cause of back and neck pain- I’m sure you or someone you know has suffered from a ‘slipped disc’ and will agree it’s not pretty.

Firstly let me say- discs don’t actually slip! I don’t know who coined the phrase but it’s misleading- the discs are incredibly strong structures which are anchored in place by thick fibrous ligaments and they aren’t ‘slipping’ anywhere. So saying, discs are perfectly capable of getting torn, inflamed, herniated, squashed or developing protrusions, bulges and extrusions. For a number of years the medical consensus on spinal pain was that the disc was public enemy number one. Patients with back pain were sent off for x-rays and MRI’s to identify which disc was the problem and then the offending disc was dealt with, often with surgery. It was all nice and neat and tidy except for the inconvenient fact that at the end of this long, expensive, and painful process quite a few of the patients still had their back pain.

Then in 1994 some clever researchers did a ground-breaking study where they took MRI’s of 98 people who didn’t have (and hadn’t previously had) any back pain. They sent these MRI films to two different radiologists to interpret without telling them that they were taken from asymptomatic people. The results were shocking! Of the 98 people in the study only 36% of them had normal discs. 52% of them had a disc bulge in at least one level, 27% had what was classed as a protrusion (a more severe bulge) and 1% had an extrusion (a very severe bulge). There were also several different non-disc related joint problems that were picked up in over 20% of the participants. Once again remember these are people with totally pain free backs.

Another study done on people without neck pain has shown very similar findings. In this one 497 people who had no current or past episodes of neck pain were given MRIs which were then examined by an impartial radiologist. Once again a surprising proportion of these people with healthy necks showed up with diagnosable problems. 17% of men and 12% of women in their 20’s had signs of disc degeneration. And for those over 60 an amazing 86% of men and 89% of women had disc degeneration. Once again keep in mind these are totally pain free people with all this disc damage.

The findings of these studies really surprised everyone. It seems so intuitive and logical that damaged discs should cause back pain that no-one had really questioned it until these researchers. Please understand that spinal discs certainly can and do cause pain and MRI’s certainly can and do give useful information – but it’s not as clear cut as anyone thought it was. More modern research is high-lighting the fact that spinal pain is a very complex condition which involves structural, immunological, psychological and neurological factors.

I’ll have to save that for another day but here are some take home points:

- MRI scans are useful but have definite limitations

- Having a bulging disc in your back doesn’t mean that this is the cause of your pain- it might well have been there for decades never causing any problems.

- Spinal discs don’t slip