Bone Scan Post Knee Replacement

Submitted by Medical Health Test Team on October 18, 2012

Knee replacement is a surgical procedure which involves replacing the surfaces of your knee joint which are worn, diseased, or damaged, with artificial surfaces. The joints are resurfaced with materials that are strong and durable and produce very little friction. Individuals who opt for this procedure can go back to activities that are moderately challenging such as golf, cycling, and cycling. A bone scan after a knee replacement surgery helps in the diagnosis of infection or loosening of the joint.

Bone scan after knee replacement can be of several types. The most routinely done procedure uses Technetium Diphosphonate (TDP). The technician or doctor injects radioactive material intravenously and your entire body is scanned a couple of hours later. This test is useful as it helps doctors diagnose if your knee implant has loosened. It is also beneficial in identifying any hairline bone fractures which do not easily show up on an x-ray. Technetium is a dye that your bone absorbs quite rapidly and it is quite safe. It is also quite easily cleared from the body through your kidneys. This bone scan is extremely sensitive and would pick up any abnormalities very easily. The negative aspect of this scan is that it might not make a specific diagnosis. Bone scans also always show up positive in the first two years after the joint is initially replaced. You doctor may order a Gallium scan if he or she is concerned that there is some infection.

Another bone scan that your doctor might order if he or she suspects any infection is an Indium-111 Radioisotope Scan. During this procedure, some of your blood is removed and re-injected into your body after it is labeled with an isotopic material. You will need to go back the next day to scan the joint. This procedure is relatively new and doctors use it in combination with other scans. The isotopic agents that are used during this process are fairly harmless and the amount of radiation is quite low. In some cases doctors might prefer to use a blood laboratory test to help in the diagnosis of an infection. These tests are helpful to a great extent, but may not be diagnostic. When these tests are combined with some other tests they would help in diagnosis any infection.

Magnetic Resonance Imaging (MRI) can also be used after the knee replacement surgery. This is done with the help of huge magnets and does not involve any radiation. The advantage of using an MRI scan is that there is no contra-indication in spite of the fact that metal is used to make part of the implant.

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