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Home > My Orthopaedist Ordered a White Blood Cell (WBC) Radioactive Labeled Bone Scan for Me. Why ?

My Orthopaedist Ordered a White Blood Cell (WBC) Radioactive Labeled Bone Scan for Me. Why ?

Dr. Jeffrey Carlson

Jeffrey R. Carlson, MD

As a practicing Orthopaedist in 2021, I have a plethora of diagnostic tests available to me when I am trying to make an accurate diagnosis of a patient’s musculoskeletal condition.  Some tests I use every day, like x-ray, and some I use less frequently, like the White Blood Cell Radioactive Labeled Bone Scan.  In this article, I will discuss the WBC Labeled Bone Scan (for short), what it is, why it is ordered and what you should expect if your physician orders one for you.

First, let’s review some facts about our blood cells.  All our red blood cells, most of our white blood cells and platelets are produced in our bone marrow.  Some specialized white blood cells (lymphocytes) are produced in the spleen and lymph nodes and T cells are born and age in the thymus gland.  We know that red blood cells carry oxygen to the tissues and carbon dioxide away, and that white blood cells fight infection, cancer, and other threats, such as allergens.

When the body has an infection, cancer, or another threat, it rushes white blood cells to fight off the problem.  After a few days, without much assistance from us, the white blood cells do their job.  But sometimes, that’s not the case. When any infection, whether minor or major, no matter the site of its genesis, gets out of control, it can eventually move to a bone and set up housekeeping. A bone infection is called osteomyelitis and it is not a good thing. Thankfully, it is somewhat rare and can be treated.

Typical symptoms of osteomyelitis are redness, swelling, pain, fever, chills, and fatigue. Certain health conditions, such as diabetes with foot ulcers, kidney disease, or those who smoke have a higher risk.  During a consult, I will ask about a prior joint replacement, inflammatory bowel disease, a port or permanent catheter, a recent surgery, an open fracture, a deep puncture wound, such as a dog bite, etc., as being a possible cause or point of entry for infection.

Because osteomyelitis is such a big deal, I want to be certain my patient is dealing with a bone infection and to know what type of infectious agent I’m fighting.  That’s when I will order the WBC Labeled Bone Scan.  This diagnostic test must be done at a hospital because it is a nuclear medicine scan, and most physician offices aren’t equipped with the specialized camera, “hot lab” nor staffed to handle radioactive isotopes.

The test involves drawing blood from the patient, spinning the blood down in a centrifuge, twice, until the white blood cells can be isolated.  Then the WBCs are “tagged” or labeled with the radioactive isotope and then reinjected into the patient’s body.  Since WBCs do what they do, they will again travel to the site(s) of inflammation or infection in the patient’s body.  At a certain timeframe after the reinjection, depending on the radioactive isotope used and its half-life, the patient will be put through a PET scanner or under a Gamma camera, as these are the two main types of cameras used in bone scintigraphy.  The bone(s) illuminated by the decay of the radioactive isotope-bearing WBCs will be able to be visualized quite well by the radiologist and the results of the scan will be sent to me.

If I get a definitive diagnosis of osteomyelitis, surgery is almost always required to treat the condition.  This is in addition to at least six weeks of IV antibiotics.  Just how extensive the surgery will be depends on the severity of the infection.  Here is the process I will go through in treating the patient surgically:

  1. Draining and debridement – This is where I will surgically open the skin and go down to the bone and the area of infection, drain the site of pus, fluid, and remove any diseased bone and tissue.  I will also take a bit of healthy bone and tissue to leave a margin, kind of like they do in Moh’s surgery for skin cancer.
  2. Depending on the severity of the infection, I can either put in a bone graft, some muscle or skin or other tissue in the place of the removed bone.  I want to restore blood flow to the area so that it will heal.  Sometimes, I will have to put a temporary spacer in place until the patient is healthy enough to have a permanent graft put into place.
  3. If the bone infection is around surgical plates, screws, rods, or a prosthetic implant, I may have to remove all hardware, and depending on the severity of the infection, either replace the hardware or put in spacers.
  4. For very severe infections that are spreading and for which antibiotics are not effective, amputation of the limb may be the only viable option to keep the infection from spreading further.

As you can see, having a bone infection is no laughing matter, and one for which specialized diagnostic testing, such as the White Blood Cell Radioactive Labeling Bone Scan, may be required to get a definitive diagnosis.

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