What is the role of bone scans in the workup of avascular necrosis (AVN)?

Updated: Dec 05, 2020
  • Author: Sunny B Patel, MD; Chief Editor: Herbert S Diamond, MD  more...
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Answer

In early AVN, osteoblastic activity and blood flow are increased; thus, the sensitivity of radionuclide bone scan is better than that of plain films at this stage.

The central area of decreased uptake is surrounded by an area of increased uptake. This phenomenon is known as the doughnut sign and indicates the reactive zone surrounding the necrotic area.

Limitations of bone scan include the following:

  • In early AVN, bone scan is less sensitive than MRI

  • Findings are nonspecific

  • Results are difficult to interpret if disease is bilateral; in unilateral disease, the healthy side can be used for comparison


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