Lumbosacral spine x-ray
A lumbosacral spine x-ray is a picture of the small bones (vertebrae) in the lower part of the spine, which includes the lumbar region and the sacrum, the area that connects the spine to the pelvis.
X-ray - lumbosacral spine; X-ray - lower spine
How the test is performed
The test is done in a hospital x-ray department or your health care provider's office by an x-ray technician. You will be asked to lie on the x-ray table in different positions. If the x-ray is being done to diagnose an injury, care will be taken to prevent further injury.
The x-ray machine will be placed over the lower part of your spine. You will be asked to hold your breath as the picture is taken so that the image will not be blurry. Usually three to five pictures are taken.
How to prepare for the test
Inform the health care provider if you are pregnant. Remove all jewelry.
How the test will feel
There is rarely any discomfort when having an x-ray, although the table may be cold.
Why the test is performed
Often, a health care provider will treat a person with low back pain for 4 to 8 weeks before ordering an x-ray.
The most common reason for lumbosacral spine x-ray is to look for the cause of low back pain that:
- Occurs after injury
- Is severe
- Does not go away after 4 to 8 weeks
- Is present in an older person
What abnormal results mean
Lumbosacral spine x-rays may show:
- Abnormal curves of the spine
- Abnormal wear on the cartilage and bones of the lower spine, such as bone spurs and narrowing of the joints between the vertebrae
- Cancer (although cancer often cannot be seen on this type of x-ray)
- Signs of thinning bones (osteoporosis)
- Spondylolisthesis, in which a bone (vertebra) in the lower part of the spine slips out of the proper position onto the bone below it
Though some of these findings may be seen on an x-ray, they are not always caused by a person's back.
Many problems in the spine cannot be diagnosed using a lumbosacral x-ray, including:
What the risks are
There is low radiation exposure. X-ray machines are checked on a regular basis to make sure they are as safe as possible. Most experts feel that the risk is low compared with the benefits.
Pregnant women should not be exposed to radiation, if at all possible. Care should be taken before children receive x-rays.
There are a number of back problems that an x-ray will not detect because they involve the muscles, nerves, and other soft tissues. A lumbosacral spine CT or lumbosacral spine MRI are better options for soft tissue disorders.
Stevens JM, Rich PM, Dixon AK. The spine. In: Adam A, Dixon AK, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 60.
Chou R, Qaseem A, Owens DK, Shekelle P; for the Clinical Guidelines Committee of the American College of Physicians. Diagnostic imaging for low back pain: advice for high-value health care from the American College of Physicians. Ann Intern Med. 2011;154(3):181-189.
Last reviewed 2/7/2011 by Linda Vorvick, MD, Family Physician, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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