Avascular Necrosis of the Bone (Osteonecrosis)

Snapshot

• A 56-year-old woman presents to the emergency department with left groin and thigh pain. She reports her pain has progressively worsened over the course of a few days and denies any trauma to the region or history of falls. Medical history is significant for systemic lupus erythematosus (SLE) treated with hydroxychloroquine and was recently placed on a short course of oral prednisone. She has had a number of SLE flairs requiring steroid therapy. On physical exam, there is decreased passive and active range of motion of the hip. Magnetic resonance imaging of the affected area demonstrates serpiginous peripheral sclerosis with inner granulation tissue highly suggestive of osteonecrosis of the left femoral head.

Introduction

• Clinical definition
  • reduced vascular supply to the bone resulting in progressive and painful degeneration of the bone
    • also termed osteonecrosis
• Epidemiology
  • incidence
    • typically occurs in the anterolateral femoral head
  • demographics
    • dependent on the cause of osteonecrosis
      • e.g., systemic lupus erythematosus associated with osteonecrosis is more likely to be seen in women
• Etiology
  • traumatic
    • fractures
      • e.g., femoral head, femur, and scaphoid bone
    • dislocation
      • e.g., slipped capital femoral epiphysis
  • atraumatic
    • idiopathic (Legg-Calve-Perthes disease)
    • alcohol use
    • corticosteroids
      • think of disorders that use corticosteroids such as
        • systemic lupus erythematosus
        • acute lymphoblastic leukemia
        • transplantation
    • Gaucher disease
    • sickle cell disease
    • caisson disease (“the bends”)
• Pathogenesis
  • impaired blood supply leads to infarction of the associated bone and bone marrow
    • vascular insufficiency can result form
      • mechanical blood vessel injury
      • blood vessel compression
      • venous occlusion
      • thromboembolism
• Prognosis
• dependent on the extent of the lesion

Presentation

• Symptoms
  • asymptomatic
    • seen in a small portion of patients
  • pain 
    • groin pain suggests osteonecrosis of the femoral head
      • thigh and buttock pain is also suggestive
    • pain in weight bearing joints
    • pain can occur at rest and at night
• Physical exam
  • non-specific
    • limited passive and active range of motion of the hip joint with hip involvement
• a limp can be seen

Imaging

• Radiographs
  • indication
    • perform in patients with a clinical presentation concerning for osteonecrosis
• Magnetic resonance imaging (MRI)
  • indication
    • gold-standard for the diagnosis of osteonecrosis
  • modalities
• without contrast

Studies

• Making the diagnosis
• based on clinical presentation and imaging findings

Differential

• Stress fracture
• Degenerative joint disease

Treatment

• Management approach
  • to preserve the native joint as long as possible
• treatment modalities is dependent on the location and extent of disease

Complications

• Collapse of femoral head in cases of femoral involvement
• Degenerative joint disease
• Focal osteoporosis