How is avascular necrosis (AVN) diagnosed?

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

No laboratory test findings specifically suggest or confirm the presence of avascular necrosis (AVN). Plain radiographic findings are unremarkable in early stages of AVN. Nevertheless, the American College of Radiology (ACR) considers x-ray of the pelvis and hips the most appropriate initial imaging study in patients at risk for AVN who present with hip pain. [19] If radiographs are normal or show femoral head lucencies suspicious for osteonecrosis, magnetic resonance imaging (MRI) of the hips without contrast is most appropriate. [19]

The ACR advises that MRI is the most sensitive and specific imaging modality for diagnosis and provides optimal evaluation of the likelihood of articular collapse. Involvement of greater than 30-50% of the femoral head, often in the sagittal plane, indicates significantly increased risk of articular collapse. [19]

Additional ACR recommendations include the following [19] :

  • Contrast-enhanced MRI may be needed to detect early osteonecrosis of the hip in pediatric patients, which is indicated by hypoperfusion
  • In patients with a contraindication for MRI, alternative imaging modalities are computed tomography (CT) or bone scintigraphy with single-photon emission CT (SPECT)

For more information, see Imaging in Avascular Necrosis of the Femoral Head.

Histology is the criterion standard for diagnosis of AVN. However, bone biopsy is not routinely performed because of the availability of sensitive noninvasive tests such as MRI.


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