Nuclear Medicine Bone Scans, but NOT DEXA Scans, for Coccyx Pain, Tailbone Pain

Regarding “Bone Scans” for Tailbone Pain, Coccyx Pain…
Someone recently asked me to explain the difference between a DEXA Scan and a Nuclear Medicine Bone Scan.
  • DEXA: A dual energy X-ray absorptiometry (DEXA) scan, also called a bone density scan, is a common technique used to measure bone density. This test is basically done to assess for osteoporosis. I do not believe that there are any “normal values” that have been established/published for the expected bone density at the coccyx. Typically the DEXA scan is done at the lower back (lumbar spine) and hip bones. I have never heard of a DEXA scan being used at the coccyx and I do not think that it would have any role there. So, in general, if someone’s “bone scan” was a “DEXA” scan (or a “bone density” scan), then it almost certainly was NOT being done to evaluate the coccyx.
  • Nuclear medicine bone scan (such as a technetium 99m scan): this is a nuclear medicine study sometimes used to assess for problems of the brain, heart, bones, etc. It can be helpful sometimes at looking at blood flow to a given area, and essentially the radioactive material is generally injected into the bloodstream and the SPECT test is used to show the blood flow to different areas. Sometimes an area of abnormality may have increased blood flow, for example, which can then be detected because you can see the increased amount of the radioactive material going to the area of increased blood flow.

    • Regarding SPECT: This is essentially a combination of a nuclear medicine bone scan plus a CT scan (computerized tomography scan), to show additional details at bones.
    • Typically, if there is evidence of an abnormality on the x-rays, MRI, or CT scan, and if there is concern as to whether this might be something more worrisome (such as cancer within the bone, or infection within the bone), then a nuclear medicine bone scan can sometimes be done to look further at whether the suspicious site essentially seems hyperactive. Basically, it can be done to try to assess whether the “abnormality” seen on the x-rays or MRI or CT scan is something more ominous, or not. For example, sometimes the bone scan will show an underlying cancer (malignancy) or bone infection (osteomyelitis).
    • Overall, it is probably less than 1% of patients with coccyx pain that will need a nuclear medicine bone scan. But in those few cases, it can be very important.
  • The most challenging situations are sometimes those where the results are not definitive (meaning that the tests are not able to conclusively determine whether a given site is normal or abnormal). Or,there are  instances where there is a notable “abnormality” such as a cyst or other finding within the bone, as seen on the x-rays or MRI or CT scan, but where it remains unclear what is “causing” that to be there. An aggressive approach would be to do a bone biopsy at that site, so that tissue could be sent to the pathology department to make sure that it is not a cancer. But, such procedures are painful and they do have their own risks as well. Also, sometimes even a biopsy can fail to give a conclusive diagnosis. Challenging topic.
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– Patrick Foye, M.D., Director of the Coccyx Pain Center, New Jersey, United States.

Patrick Foye, M.D.
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