Pediatric Avascular Necrosis

  • Etiology: Ischemia leading to death of bone
  • Imaging MRI: Most sensitive modality demonstrating changes well before radiographic changes are visible
    — Reactive interface line: Focal serpentine low signal line with fatty center is most common appearance and first sign on MRI
    — Double line sign: T2WI serpentine peripheral or outer dark (sclerosis) and inner bright (granulation tissue) line is diagnostic for avascular necrosis
    — Rim sign: Osteochondral fragmentation
    — Diffuse edema: Edema occurs in advanced stages and is directly correlated with pain
    — Secondary degenerative change such as osteoarthritis
    — Non-viable marrow does not enhance
  • DDX:
  • Complications:
  • Treatment: Conservative
  • Clinical: Commonly seen in patients with malignancy who are on steroids

Radiology Cases of Avascular Necrosis

Radiology Cases of Avascular Necrosis of Humerus

MRI of pediatric avascular necrosis of humerus
Sagittal T1 MRI without contrast of the humerus (left) shows a lesion in the proximal humerus to be defined by a focal serpentine low signal line with fatty center (reactive interface line) while sagittal STIR MRI (right) shows the lesion in the proximal humerus to be defined by a serpentine outer dark line and an inner bright line (double line sign).

Radiology Cases of Avascular Necrosis of Knee

Radiograph and MRI of avascular necrosis of the knee
AP (above left) and lateral (above right) radiographs of the knee shows a serpiginous sclerotic lesion in the distal femur. Coronal T1 MRI without contrast of the knee (below left) shows the lesion in the distal femur to be defined by a focal serpentine low signal line with fatty center (reactive interface line) while coronal T2 MRI (below right) shows the lesion in the distal femur to be defined by a serpentine outer dark line and an inner bright line (double line sign).
MRI of avascular necrosis of knee
Sagittal T1 (left) and STIR (right) MRI without contrast of the knee show a large knee joint effusion along with well demarcated serpiginous lesions in the distal femur and proximal tibia that on STIR images demonstrate the double line sign.