Bone Scans

June 5, 2012
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The last imaging technique we’ll discuss will be different types of full body scans available, specifically used by podiatrists to determine if bone infection is present.

A scan, either for bone or WBCs (white blood cells), is done by injecting a very small amount of a specific type of radioactive dye into a vein. This dye will then spread through the body as the blood is pumped through all the bone, muscle and internal organs. The dye contains a certain substance that will bind to somewhere in the body. The dye for bone scans binds to bone that is currently being remodeled. The dye for WBCs will search out WBCs and bind to them. The person is then scanned at different time intervals with a gamma camera, which is able to detect where the most activity is concentrated. This can be very useful in diagnosing foot conditions.

When it comes to podiatry, these scans are primarily useful with diabetic patients. Diabetic patients struggle with two conditions, osteomyelitis (bone infection) due to ulceration, and Charcot Foot (a non-infected bone destructive process). These two conditions are sometimes difficult to tell apart clinically. With infected bone, both a bone and WBC scan will be positive, whereas only a bone scan will be positive with Charcot. Bone scans can give the podiatrist clues to which process if going on. Scans are generally cheap tests and readily available.

A downside to bone scans is that they are not very specific. There are many conditions that will have a positive bone scan. A fracture, infected bone, growth plates, arthritis etc. will all give positive bone scans. So even if I suspect bone infection, and the bone scan comes back as positive, I still have to perform other tests to confirm my suspicions. There could be another underlying condition giving the positive bone scan test. This obviously limits their usefulness. Some types of scans are technically difficult to perform, and others are difficult to read. Scans also expose the patient to some radiation, thus making it necessary to make sure these scans are not ordered unless absolutely necessary.

Imaging techniques used by podiatrists are essential in determining the source of patient’s complaints. These techniques are very safe when used in the appropriate situations.

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