Lower Back Pain Investigations - Lumbar Spine MRI scans and X-Rays

There are some lower back pain investigations that are very commonly used in the management of lower back pain. Most people with lower back pain, very understandably, want to know what is causing it. Doctors often order these examinations in the hope that they will help them pin down the cause of the problem and provide a diagnosis.

The most common of these lower back pain investigations include:

• X-Ray
• Magnetic Resonance Imaging also called MRI scans
• CT Scans (much less common)

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Lumbar X-Ray

X-Rays are very good at showing up bony problems such as fractures and dislocations. They are also good at showing age (degenerative) changes in the joints and the vertebrae. They can show if there has been movement of one vertebrae on another (spondylolisthesis). However, soft tissues such as muscles and ligaments are not seen on X-ray and neither are discs, an X-ray will only show a gap or the space a disc occupies. Whilst this can give a suggestion of disc problems if the space is reduced or narrower than expected, it will not show a disc bulge or nerve root irritation. You cannot diagnose sciatica from an X-ray. So this type of test is really good at ruling out serious problems like fractures, but is poor at giving exact causes. Changes of age are common findings. Despite this X-rays are a very commonly used lower back pain investigation.

X-Ray showing the gap or disc space (image courtesy wikimedia commons)

Film showing a slip or spondylolisthesis (image courtesy wikimedia commons)

Lumbar Spine MRI Scans

MRI scans work by placing the part to be imaged in a powerful, uniform magnetic field. This allows images in 'slices' to be viewed. Unlike X-ray this test gives a clearer idea of soft tissue structures such as discs, ligaments and the spinal cord and nerve roots. Examples of MRI film are shown here.

MRI scan of lower back (MB Collection personnelles) CC-BY-SA-2.5, via Wikimedia Commons)

MRI of an L4-l5 disc herniation (By Edave (Own work) [see page for license], via Wikimedia Commons

CT Scans

You may also have heard of Computed Axial Tomography also called CAT or CT scan. A CT scan is a type of X-ray that allows a three dimensional image to be produced from large numbers of two dimensional images. It is mainly used to look at the brain, chest and abdomen and for complex fractures. It is rarely used in the UK for lower back pain investigations.

Functional MRI

This is a newer technology that lets us see what is happening inside the brain when the body is stimulated in some way. it is used increasingly in research and is helping us understand a lot more about pain.

How do Lumbar X-Rays and MRI scans help?

When someone has been diagnosed with the most common type of back pain called simple or non-specific, tests such as X-rays and MRI scans often show very little wrong - aside from the usual changes of age that are very common and are not always associated with pain.

Here are some things we know about MRI scans and lower back pain:

1. The things most often seen are changes of age or degenerative changes; these are common findings even in quite young people. Disc bulges are another very common finding.
   
   
2. These findings are as common in people with no back pain as they are in people with back pain.
   
   
3. There is no relationship between the findings on MRI and either the likelihood that you will get back pain, the severity of your symptoms or the likely outcome following an episode of back pain.
   
   
4. MRI scans taken before someone had back pain and after they got it look exactly the same.
   
   
5. MRI can be helpful to identify problems that may need surgery e.g. disc bulges causing nerve root irritation.

In most guidelines for the management of Lower Back Pain, MRI is not recommended unless the diagnostic triage suggests serious spinal pathology or nerve root involvement (see reference 1 below)  

"Structural changes seen on MRI appear to be as common in asymptomatic individuals as in people with Lower Back Pain and are, therefore, considered of little value in either explaining the cause of pain or deciding the subsequent course of management" (1 )

If there is any doubt that you may have a serious problem or a nerve root irritation then an MRI may be helpful. You need to discuss this with your healthcare provider who will help you make this decision.

This information may seem a bit surprising - we believe in the value of these lower back pain investigations and tests and trust that they will tell us useful information - indeed, used appropriately they can be very helpful and are essential where there is a suspicion of serious problems. In practice they should not be routinely performed for simple low back pain. An exception may be when someone is very worried that they have a serious back problem and an MRI may be reassuring to them.

This article above is another helpful way to look at the problem. In this study outcomes from both MRI and X-ray were similar but in the MRI group the doctor felt a bit more reassured.

 

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The best way to diagnose simple lower back pain is by seeing a health care professional who will take a full history and examine you. The combination of these two things should be enough to allow an experienced clinician to make a diagnosis that you can trust. If there is any doubt that you may have more serious problems than further lower back pain investigations can then be arranged.

References

1.Kleinstck et al. Are structural abnormalities on magnetic resonance imaging a contraindication to the successful conservative treatment of chronic non-specific low back pain? Spine, 1 Sep 2006, vol. 31, no. 19, p. 2250-7

2.Carragee et al Are first-time episodes of serious LBP associated with new MRI findings? The spine journal: official journal of the North American Spine Society, Nov-Dec 2006 ,vol. 6, no. 6, p. 624

3Non Specific or Simple Lower Back Pain Guidelines

4. Chou R et al. Diagnosis and treatment of low back pain: a joint clinical practice guideline from the American College of Physicians and the American Pain Society. Ann Intern Med. 2007 Oct 2;147(7):478–91.

 

Lower Back Pain Toolkit Home Page

For a greater understanding of the value of lower back pain tests read about the different causes of lower back pain.

 

29-Jul-2017