What is the role of radiography 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

Plain radiographic findings are unremarkable in early stages of AVN. Nevertheless, the American College of Radiology considers x-ray of the pelvis the most appropriate initial imaging study in patients at risk for AVN who present with hip pain.Both an anteroposterior view of the pelvis and a frog-leg lateral view of the hip are necessary, as articular collapse or cortical depression may be seen on only one of those projections. [19]

In children, the earliest radiographic findings of AVN include the following [19] :

  • Smaller ossific nucleus
  • Increased radiodensity
  • Subchondral fracture
  • Metaphyseal radiolucencies.

Subsequentl findings in pediatric patients include fragmentation, resorption, reossification, and remodeling of the femoral head and neck. [19]

In mild-to-moderate AVN, radiographs demonstrate sclerosis and changes in bone density. In advanced disease, bone deformities, such as flattening, subchondral radiolucent lines (crescent sign), and collapse of the femoral head, are evident (see images below).

Avascular necrosis in the femoral head resulting from corticosteroid therapy.

Avascular necrosis in the femoral head resulting f Avascular necrosis in the femoral head resulting from corticosteroid therapy.

Avascular necrosis of the shoulder showing subchondral radiolucent lines (crescent sign).

Avascular necrosis of the shoulder showing subchon Avascular necrosis of the shoulder showing subchondral radiolucent lines (crescent sign).

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