DESCRIPTION

• Avascular (aseptic) necrosis results from bone blood supply interruption (either traumatic or nontraumatic occlusion).
• The femoral head is the most common site.
• A self-limiting idiopathic avascular necrosis of the hip that occurs in children is known as Perthes disease (see “Perthes Disease”).

ETIOLOGY

• Traumatic
  • Slipped capital femoral epiphysis
  • Hip fracture
  • Hip dislocation
  • Complication of casting, bracing, surgery
• Nontraumatic
  • Glucocorticoid or chemotherapy
  • Malignancy (leukemia)
  • Idiopathic (older, after physeal closure); similar to adult avascular necrosis
  • Idiopathic (younger, before physeal closure, Perthes disease)
  • Dysbaric osteonecrosis (Caisson disease)
  • Sickle cell disease
  • Septic arthritis
  • Gaucher disease
  • Viral infection (HIV, cytomegalovirus [CMV])
  • Radiation therapy
  • Hypercoagulable states
  • Hypothyroidism
  • Growth hormone deficiency (before and during growth hormone therapy)

RISK FACTORS

Age

• The age of the child at onset of avascular necrosis is a strong prognostic indicator of outcome.
• Glucocorticoid-induced avascular necrosis is more common in children ≥8 years of age.

PATHOPHYSIOLOGY

• Death and necrosis of bone with gradual blood supply return
• Necrotic bone gradually resorbed and replaced by new bone, but there is a disconnect between bone resorption and formation leading to net bone loss.
• During bone resorption, structural integrity of femoral head may be reduced, leading to collapse.