Is an MRI or X-ray the best scan for lower back pain?
Sciatica, discs, joint pain? Includes Case Studies
31/03/2023 by Jess Kenney DC MChiro
(Approx 2-4 minute read)
In short:
X-ray and MRI are two types of scan that are used to look for anything structural that can be causing pain inside the body. They should be used as part of the whole clinical picture including the patient history, and neurological and orthopedic examination.
Imaging alone is not always enough to form the correct diagnosis.
What is an MRI?
MRI (Magnetic Resonance Imaging) uses powerful magnets and radio-waves circling the body to assess bones, soft tissue, swellings, spinal discs, nerve lesions and cartilage. Due to the way MRI’s work, it is not always an option for people that have metal fragments in their body including shrapnel or pacemakers, however titanium objects are not a problem. There will be multiple images both vertical and horizontal through the body which are pieced together to find issues correlating to the symptoms.
The scan is normally performed laying on a table in a tube, it takes around 20 minutes and the machine is quite noisy so is usually headphones available. It is completely pain free and non-invasive, with no known side effects from the scan.
There are alternative types of MRI that are upright and/or open however there are not many of these machines in the UK. The benefits of having an open scanner is that claustrophobic patients may feel more comfortable, and upright scanners allow the radiographer to assess the structures under weightbearing circumstances, which is particularly useful if the symptoms only occur in certain positions.
Something important to remember...
Disc bulges can change throughout the day and by position. Having an MRI on a pain-free day in your comfort position may not show problems that would show up on a pain day in a pain position.
What is an X-ray?
X-ray uses low level radiation to look at looks at very high or low density objects such as bone concerns or air/fluid in the lungs. . On an X-ray scan, metal shows up white, bone shows grey and air/fluid shows black. Soft tissue injury will not show up on X-ray, however we can see the space where nerves, discs, soft tissue and vessels should sit and see if there is an obvious obstruction. X-ray is quicker, cheaper and easier than MRI.
Standing is the most common position for X-ray although some may be laying, and they are very quick as taking the images is instant. There will be one view from the front and one from the side to avoid misinterpretation (demonstrated in the case study).
It is possible to adapt an X-ray to highlight areas of joint instability by performing the X-ray with the patient in different planes of movement. For assessing a patient with suspected lumbar instability, the patient would have a lateral X-ray in neutral, lumbar extension (leaning back) and lumbar flexion (leaning forwards).
Something important to remember:
X-ray findings are very slow changing and do not change throughout the day. If you've had pain for 2 weeks but the Xray come back with degenerative change, it is highly unlikely this is the sole source of your pain.
Can you get false positives with X-ray or MRI?
As with all types of imaging, you can get false positives. This means a finding on scan is interpreted as being a problem when it is actually incidental and not causing any problems. The most common false positives are the diagnoses of arthritis, degenerative conditions, disc bulges or tears in cartilage.
While these may exist on the scan, they are not always the source of the pain and to identify whether they are, the scan findings must correlate with the patient history and entire clinical picture.
Neither MRI or X-raywill show a movement disorder or instability which are commonly overlooked sources of pain, especially if there is something visible, albeit incidental, on imaging.
Are there any other options apart from X-ray or MRI?
Ultrasound: This is the same type of scan you’d use to look at a baby. It can see soft tissue and fluid but can’t pass through bone, making it good for superficial tendon damage, cysts and kidneys but not useful for looking at the spine, discs, nerves or inside the joints. There are types of Ultrasound which will identify instability.
CT: This is a type of X-ray that gives a 3D x-ray. Its very good for looking at awkward bone fractures or any high density concerns.
Flexion-Extension X-ray: This is the type of X-ray where the images are repeated with the patient in different positions.
Is X-ray or MRI better for lower back pain?
Determining which is the best scan depends on several factors:
What are the symptoms?
Are there any signs of significant nerve damage or tears in cartilage? MRI is Gold standard testing for hip, shoulders, trapped spinal nerves including sciatica, spinal discs and knees. X-ray is the quicker, easier, and cheaper scan and will identify most common concerns.
Will it change the immediate outcome measures?
If you have 2 diagnosis options but the treatment plan remains the same, is it worth the scan right now?
Will it change the long term outcome measures?
If you suspect a degenerative process is causing the pain and this episode is manageable with conservative care, at what point is it worth getting the scan?
Is there any contraindications?
If there are any pieces of magnetic metal or batteries in the patients body, they will not be able to have an MRI. Are they claustrophobic? Can they lay on their back? Have they received an excessively high amount of radiation before?
Cost vs Worth?
Cost is something tangible. Worth depends on the patient preference, immediate treatment outcomes and long term expectations. For cost - an X-ray organised through the clinic is £45. An MRI organised through the clinic is £200 for a 7 day turnaround, although this can increase to £500-600 at certain hospitals, or more if you choose an open or upright scanner.
What is the risk of a false positive?
Common false positives include disc bulges, arthritis, degenerative disc disease, degenerative joint disease, mild tears in cartilage.
Patient preference?
Some patients are claustrophobic, some would rather not know unless if was drastically going to change anything, some may hyperfocus on an incidental finding.
Mental impact?
The mental impact of being diagnosed with a chronic condition such as arthritis has negative effects on the patients wellbeing and is associated with a slower recovery.
MRI Case Study:
Lumbar disc bulge on MRI
Patient presents with severe low back episodes for 30+ years. Used to see an osteopath when having an episode to 'crack his back' which relieved pain. Gradually episodes become worse in intensity and frequency over years. Some episodic nerve symptoms in leg, but does have ongoing right knee pain for which they were also referred for a scan.
Referred for MRI (laying, pain-free day). The disc substance is dark and we see a very prominent disc bulge at L1/2 (green arrow) and degeneration through the L3/4 vertebral endplates (blue). Also noted are: minor disc bulges (pink) and loss of normal lumbar curve (purple) which may or may not be pain producers judging solely from the side view.
The MRI report including the horizontal view states the L1/2 (green) disc bulge was not pinching any nerves, however the smaller disc bulges were hitting on some nerves.
Orthopedic assessment showed a preference for flexion based movements, no nerve damage, weak lumbar muscles and restriction in the lumbar joints, right pelvic mobility and right hip mobility.
Protocol:
(dependent on patient outcomes)
Week 1-4: Flexion and decompression of the lower back, address loading and rotational axis on disc, improve mobility in mid back.
Week 4-8: Rebuild extension movement into back.
Week 8+: Strengthen, stabilise and maintain.
X-Ray Case Study:
AP lumbo-pelvic X-ray
Patient presents with with ongoing, progressive left groin pain on exercising, ongoing left knee pain and episodic lumbar tension/pain. Gradually episodic and worsening over several years. History of triathlons and regularly cycles. No nerve pain.
Orthopedic testing showed poor left hip rotation with a bony end feel, compensation in spinal movement when doing hip flexion and rotation tests and a functional short leg on left.
Lateral lumbar X-ray
AP (front) (Image to left) view of low back and pelvis shows hip arthritis (green) due to a loss if joint space at the top, although bone structure appears healthy with no bone cysts. Functional curvature of low back and pelvis (pink) - as the left hip has lost some capacity for movement, the lower back and pelvis are hiking up to compensate, causing the appearance of a curvature in the lower back.
Side View (Lateral) (Image below) gives the illusion of reduced disc heights (pink). Due to AP view we know this is the curvature in his spine superimposing the vertebrae, rather than any clinical concern of the disc heights. There is a good curve in the lower back, and some increased areas of whiteness around the spinal joints (under pink arrows) which indicates some wear and tear and again this is not of clinical concern for his symptoms.
Protocol:
(dependent on patient outcomes)
Week 1-4: Improve spinal movement and symmetry in adjustments and advice on working posture. Address hip mobility through passive and active range of movement in adjustments with addition of daily home exercises to stretch and strengthen.
Week 4-8: Strengthening and stabilising for hip and low back to reduce the compensation in lower back.
Ongoing: Monitor hip and speak to consultant if further action required or desired by patient.
Research:
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Botchu R, Bharath A, Davies AM, Butt S, James SL. Current concept in upright spinal MRI. Eur Spine J. 2018 May;27(5):987-993. doi: 10.1007/s00586-017-5304-3. Epub 2017 Sep 21. Erratum in: Eur Spine J. 2018 Feb 26;: PMID: 28936611.
Healy, John F.; Healy, Barbara B.; Wong, Wade H. M.; Olson, Eric M.. Cervical and Lumbar MRI in Asymptomatic Older Male Lifelong Athletes: Frequency of Degenerative Findings. Journal of Computer Assisted Tomography 20(1):p 107-112, January 1996.
W. Brinjikji, P.H. Luetmer, B. Comstock, B.W. Bresnahan, L.E. Chen, R.A. Deyo, S. Halabi, J.A. Turner, A.L. Avins, K. James, J.T. Wald, D.F. Kallmes, J.G. Jarvik.. Systematic Literature Review of Imaging Features of Spinal Degeneration in Asymptomatic Populations. American Journal of Neuroradiology Apr 2015, 36 (4) 811-816; DOI: 10.3174/ajnr.A4173
Hobusch GM, Fellinger K, Schoster T, Lang S, Windhager R, Sabeti-Aschraf M. Ultrasound of horizontal instability of the acromioclavicular joint : A simple and reliable test based on a cadaveric study. Wien Klin Wochenschr. 2019 Feb;131(3-4):81-86. doi: 10.1007/s00508-018-1433-x. Epub 2019 Jan 7. PMID: 30617708; PMCID: PMC6394808.
Remember:
Imaging does not always give you the whole picture. It must be taken with the whole clinical presentation.
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