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Volume 2 Issue 1 - January 2004
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When is Imaging Helpful for Patients with Back Pain?

Imaging Modalities for the Spine
Further Information

ince the lifetime prevalence of low back pain is about eighty percent, it is hardly surprising that back pain is one the most common reasons for patients to seek medical care. However, in the vast majority of cases, acute back pain (duration less than three months) is a self-limited condition that resolves with analgesic treatment and activity modification. In more than 80% of cases of back pain (Table 1) imaging will not affect treatment. However, it may lead to unnecessary additional testing due to the discovery of incidental benign lesions and nonspecific degenerative processes that may also occur in asymptomatic individuals.

In a recent study of patients with low back pain who had been referred for radiographic evaluation, only 3.7% went on to have surgery. However, the rate of surgeries performed on those who had been randomly assigned to MRI was double that of those who were assessed with plain film radiography. Furthermore, there was no difference in the outcome (functional disability and pain) in these two groups.

Nevertheless, low back pain will sometimes reflect a more serious condition than uncomplicated lumbar
Figures A and B
Figures A and B:  In a 72 year old patient with intermittent low back pain, MR images of the lumber spine show multi-level abnormalities, such as severe spinal stenosis at L3-4 and disk herniation at L5-S1, that are far more impressive than the degree of symptoms.

strain or sprain. The challenge is to identify red flags that would distinguish patients who should have a more intensive work-up. The American College of Radiology has put substantial effort into the development of criteria that may justify further evaluation of patients with imaging (Table 2).

Table 1. Pretest Probability of Disorders that Cause Low Back Pain
Lumbar strain or sprain 70%
Degenerative processes 10%
Herniated disc 4%
Osteoporotic compression fracture 4%
Spinal stenosis 3%
Spondylolisthesis 2%
Traumatic fracture <1%
Ankylosing spondylitis 0.3%
Metastatic cancer 0.7%
Spinal infections 0.1%

Non-spinal causes


Table 2. Indications for Further Evaluation by Imaging*
Recent significant trauma
Unexplained weight loss
Unexplained fever
History of Cancer
IV drug use
Prolonged use of corticosteroids
Age > 70
Duration longer than 3 months

*From American College of Radiology Criteria

Imaging Modalities for the Spine
Conventional radiography may be sufficient as a screening tool in the setting of trauma, prolonged steroid use, and osteoporosis in elderly patients because it can show vertebral compression fractures. Other imaging modalities may be warranted in the setting of suspected malignancy or infection, even if plain radiographs are negative. In patients with low back pain, the most common clinical indications for advanced imaging include radiating pain (radiculopathy, sciatica) or symptoms of nerve root compression due to cauda equina syndrome (bilateral leg weakness, urinary retention and saddle anesthesia), often reflecting disc herniation and/or spinal stenosis.

Although the appropriate selection of imaging modality can be challenging, MRI is usually the modality of choice. MRI is superior to CT for the depiction of disc abnormalities and bone marrow lesions, although CT can improve the assessment of cortical bone and, therefore, better delineate some fractures. MRI with or without contrast (gadolinium) enhancement reliably demonstrates vertebral infections and malignancy. MRI has taken over the role of isotope bone scan in the spine, but the bone scan remains important when a survey of the entire skeleton is necessary.

If MRI is contraindicated, isotope bone scan and/or CT may be substituted when there is a suspicion of

infection or malignancy. In the case of radiating pain or cauda equina syndrome, CT myelography is effective but requires lumbar puncture for the injection of iodinated contrast. When other studies fail to localize the source of pain, image-guided injections, such as nerve root block or facet block, may have diagnostic value.

Figures C and D
Figures C and D:  In a 52 year old patient with known lung carcinoma, MR images show two focal lesions (L1 and L4) that enhance densely after contrast administration.  Radiographs were normal in appearance.  Back pain was the first indication of metastatic disease.

If emergency imaging for back pain is warranted, the patient should be sent to the Emergency Department at MGH, where radiography, MRI, or CT will be performed. In other cases, imaging can be performed at MassGeneralWest in Waltham, Mass General Imaging in Chelsea or the main MGH campus. It can be ordered online via the Radiology Order Entry (ROE) System (http://mghroe ) or by calling 4-XRAY (617-724-9729). Results are made available to physicians online within 24-48 hours.
  Further Information
For further questions on imaging for back pain and image-guided treatments (e.g. steroid injections, vertebroplasty), please contact Dr. William Palmer, MGH Department of Radiology, at 617-726-7719 or visit

For general information regarding MGH Radiology services and locations, please contact Kristen Dean at 617-724-4902.

This article provided useful information about the appropriate use of imaging studies:

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Expert Panel on Neurologic Imaging: Anderson, RE, Drayer, BP; Braffman, B, et al. (2000) American College Of Radiology Appropriateness Criteria: Acute low back pain - radiculopathy. (Download pdf)

Borenstein, DG, O'Mara, JW, Jr., Boden, SD, Lauerman, WC, et al. (2001) The value of magnetic resonance imaging of the lumbar spine to predict low-back pain in asymptomatic subjects : a seven-year follow-up study. J Bone Joint Surg Am 83-A: 1306-11

Jarvik, JG and Deyo, RA.(2002) Diagnostic evaluation of low back pain with emphasis on imaging. Ann Intern Med 137: 586-97

Jarvik, JG, Hollingworth, W, Martin, B, Emerson, SS, et al. (2003) Rapid magnetic resonance imaging vs radiographs for patients with low back pain: a randomized controlled trial. JAMA 289: 2810-8

Jensen, MC, Brant-Zawadzki, MN, Obuchowski, N, Modic, MT, et al. (1994) Magnetic resonance imaging of the lumbar spine in people without back pain. N Engl J Med 331: 69-73