Lumbosacral spine x-ray
X-ray - lumbosacral spine; X-ray - lower spine
A lumbosacral spine x-ray is a picture of the small bones (vertebrae) in the lower part of the spine. This area includes the lumbar region and the sacrum, the area that connects the spine to the pelvis.
The spine is divided into several sections. The cervical vertebrae make up the neck. The thoracic vertebrae comprise the chest section and have ribs attached. The lumbar vertebrae are the remaining vertebrae below the last thoracic bone and the top of the sacrum. The sacral vertebrae are caged within the bones of the pelvis, and the coccyx represents the terminal vertebrae or vestigial tail.
These are the five vertebra of the lower back. The last vertebra (on the upper left of the picture) attaches to the sacrum, and the top vertebra (on the right of the picture) attaches to the thoracic section of the back. The vertebra are broader and stronger than the other bones in the spine. This allows them to absorb the added pressure applied to the lower back, but this area remains a common site of injury. The vertebra are numbered from one to five and are labeled L1, L2, L3 etc. from the higher bones to the lower.
These are twelve vertebra of the mid back. The last vertebra (on the left side of the picture) attaches to the lumbar (lower) spine, and the top vertebra (on the right) attaches to the cervical (neck) section of the back. The vertebra are broader and stronger than the cervical bones. This allows them to absorb the added pressure applied to the mid back, but they remain a common sight of injury. The vertebra are numbered from one to twelve and labeled T1, T2, T3, et cetera, from the upper most bones to the lowest.
This is the spine and the sacrum with the cervical (neck), thoracic (mid-back), and lumbar (lower back) vertebra. Notice how the appearance of the vertebra change as you look down the spine. The change in shape and size reflect the different functions of the neck, mid-back, and lower back.
The sacrum is a shield-shaped bony structure that is located at the base of the lumbar vertebrae and that is connected to the pelvis. The sacrum forms the posterior pelvic wall and strengthens and stabilizes the pelvis. Joined at the very end of the sacrum are two to four tiny, partially fused vertebrae known as the coccyx or tail bone. The coccyx provides slight support for the pelvic organs but actually is a bone of little use.
The vertebral column is divided into the cervical, thoracic, and lumbar region. It provides structural support for the trunk and surrounds and protects the spinal cord. The vertebral column also provides attachment points for the muscles of the back and ribs.
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. In most cases, 3 to 5 pictures are taken.
How to Prepare for the Test
Tell your provider if you are pregnant. Take off 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, your 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)
- Fractures
- 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 the cause of back pain.
Many problems in the spine cannot be diagnosed using a lumbosacral x-ray, including:
- Sciatica
- Slipped or herniated disc
- Spinal stenosis - narrowing of the spinal column
Risks
There is low radiation exposure. X-ray machines are checked often 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.
Considerations
There are some back problems that an x-ray will not find. That is because they involve the muscles, nerves, and other soft tissues. A lumbosacral spine CT or lumbosacral spine MRI are better options for soft tissue problems.
References
Contreras F, Perez J, Jose J. Imaging overview. In: Miller MD, Thompson SR, eds. DeLee, Drez, & Miller's Orthopaedic Sports Medicine. 5th ed. Philadelphia, PA: Elsevier; 2020:chap 7.
Kapoor G, Toms AP. Current status of imaging of the musculoskeletal system. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 38.
Parizel PM, Van Thielen T, van den Hauwe L, Van Goethem JW. Degenerative disease of the spine. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 48.
Warner WC, Sawyer JR. Scoliosis and kyphosis. In: Azar FM, Beaty JH, eds. Campbell's Operative Orthopaedics. 14th ed. Philadelphia, PA: Elsevier; 2021:chap 44.
Version Info
Last reviewed on: 4/27/2023
Reviewed by: Linda J. Vorvick, MD, Clinical Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
