21/10/2012 Gavin

XRays, MRIs and other low back pain tests

So, you’ve got a really sore lower back, and maybe pain down your leg (perhaps “sciatica”).  You go to your doctor believing the obvious thing is to send you for an XRay – or maybe if you’re lucky an MRI will be required…  But your doc is totally up to date on the Royal College of Radiologists’ guidelines for low back pain and here’s the bad news –

No investigations should be recommended routinely.  There must be a clinical indication (need) that you (or the doc) need an answer to;  the most urgent of these is to eliminate the possibility that you have a “pathology” (a disease process like cancer, osteoporosis, fracture).

It’s important to stress that finding something wrong on an investigation does not prove that that is the cause of your pain.  It may be a factor.  The investigation should be combined with knowledge gained from the case history (what you tell the doc), and the examination, to reach an evaluation.

If I appear to mention a lot of “nasty” things here it’s not because they are common.  It’s only the tiny minority of low back pain sufferers that have something “medical” wrong with them – that’s the value of investigations, to identify that small minority.  But remember, the history and the examination tells clinicians who may be in that high-risk group.  Please don’t rush out to your doctor and demand an investigation!


These old investigations are still particularly useful in looking at gross alignment of the spine e.g. spondylolisthesis (where one of the bones slips out of line).  Compression fractures (in osteoporosis or significant trauma) and some infections and tumours affecting the bones can also be seen.


These are perhaps the most useful of investigations, in that they detailed supply information in different planes (side view, front view, top-to-bottom view).  Any slice can be taken through the body by use of magnetism rather than X-Rays.  Generally MRI will give a very good view when looking for disc bulges, tumours, structural misalignment etc…

CT scan

CT scans use X-Rays from different directions to provide detailed images of slices of the body.  They are particularly useful when looking for detail of a small area, especially within bone – not so good for softer tissue.

Blood Tests

Blood tests are used to determine whether there are abnormalities within your blood e.g. high or low levels of different blood cells, or certain hormones, metabolites (your body breaks things down).
They are sometimes useful in cases of low back pain when the clinician considers it possible that you may have a “disease” causing your pain e.g. some forms of arthritis, some forms of cancer.


These studies are much less commonly used now that MRI’s are more widely available.  A dye is passed inside the spinal membranes and X-Rays or CT scans will show where there is pressure/abnormal shape within the spinal nerves.  The test is now used most commonly if you have a pacemaker (and cannot go into an MRI) or if an MRI result is not clear.

Nerve Conduction Study

This test establishes whether messages are passing normally along the length of a nerve and helps to isolate where there may be compression of a nerve.  It may be used in cases of low back pain accompanied by pain or pins and needles down the leg, or weakness in muscle.

EMG Test

This test establishes whether a muscle is responding appropriately to stimulation.  It can be used to test for various neuromuscular disorders.  It may be used in low back pain accompanied by muscle weakness.


In this test a needle is inserted into the disc and a dye injected into it.  If this increases the usual pain, it suggests some of the pain may be due to disc injury.  With the dye in the disc XRays and CT scans will reveal more about tears within the annulus.

Bone Density Tests

These are conducted in order to screen for the possibility of osteoporosis, which can cause microfractures (or bigger fractures) and pain.  The most commonly used technology is the Dexa test (Dual energy Xray absorptiometry).

So, there you have it – perhaps best just to come and speak to us first at activex clinics!  If there’s a clinical indication for further investigation, we will certainly write to your GP to request it.  But don’t assume it’s necessary.  On a cheery note, all of them come with the potential for side effects.

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