Osteonecrosis of the femoral head (Avascular necrosis of the femoral head)

Osteonecrosis of the femoral head is a consequence of insufficient vascular supply to the femoral head. Most cases are either idiopathic or associated with alcohol, corticosteroid therapy, or trauma. The condition presents with groin pain, which may radiate to the knee or ipsilateral buttock, and limited range of motion at the hip. Diagnosis is based on x-ray, followed by MRI. No curative treatments have been identified. Initial nonsurgical treatment focuses on preventing collapse of the femoral head, although surgical intervention may be required if the disease progresses. However, there is no consensus regarding the best treatment options.

For avascular necrosis of the femoral head in children, see Legg-Calvé-Perthes disease.

Several traumatic and atraumatic factors are known contribute to the etiology of osteonecrosis, all of which contribute to changes in blood supply.

• Atraumatic factors
  • Glucocorticoid use (35–40% of cases)
  • Alcohol (20–40% of cases)
  • Other
    • Smoking
    • Hemoglobinopathies (e.g., sickle cell disease)
    • Radiation
    • Myeloproliferative disorders
    • Autoimmune diseases (e.g., SLE, antiphospholipid syndrome)
    • Hyperuricemia, hyperlipoproteinemia, diabetes mellitus
    • Gaucher disease
      • Bone marrow analysis shows Gaucher cells
• Traumatic factors
  • Lateral or medial femoral neck fractures, particularly with dislocation
  • Femoral head fractures
  • Slipped capital femoral epiphysis (SCFE)

Mnemonic for possible etiologies of femoral head necrosis → ASEPTIC: alcohol, sickle cell disease/SLE, exogenous steroid, pancreatitis, trauma, infection, caisson disease (decompression sickness)

References:^[1][2][3][4]

• Slowly progressive groin pain, which may radiate to the knee or ipsilateral buttock
• Limited active and passive range of motion at the hip
• Bilateral in 50% of cases

Consider osteonecrosis in patients presenting with groin pain and a history of corticosteroid use or alcohol abuse.

References:^[1][2][3]

• X-ray (best initial test)
  • Cystic and sclerotic changes in the femoral head
  • Subchondral collapse
  • Flattening of the femoral head
• MRI (best confirmatory test) : used to the visualize necrotic-viable bone interface
• Staging
  • Evidence the bone is pre/post-collapse
  • Size of the necrotic component
  • Amount of femoral head depression
  • Acetabular involvement
  • ARCO staging
    • Stage 0 (initial stage) → normal imaging studies; histological evidence of change
    • Stage I (reversible early stage) → positive MRI, normal x-ray
    • Stage II (irreversible early stage) → X-ray and MRI positive, preserved contour
    • Stage III (transitional stage) → X-ray: subchondral fracture
    • Stage IV (late stage) → calcification, resorption cysts and formation of new cartilage in the x-ray image

Early diagnosis via MRI or scintigraphy is possible!

References:^[1][2][3]