What are the treatment options for Avascular Necrosis (AVN) of the femur?

Treatment Options for Avascular Necrosis (AVN) of the Femur

The treatment of avascular necrosis of the femoral head should be based on the stage of disease, with core decompression recommended as the primary surgical intervention for early-stage disease (pre-collapse) to prevent articular collapse, while total hip arthroplasty is recommended for late-stage disease with articular collapse. 1

Disease Staging and Risk Assessment

• Avascular necrosis is characterized by bone death due to inadequate vascular supply, commonly affecting the femoral head 1
• The extent of necrosis is a critical prognostic factor:
  • Lesions involving <30% of the femoral head have <5% progression to collapse 1, 2
  • Lesions involving >30% of the femoral head have a 46-83% risk of progression to collapse 1
• Common risk factors include corticosteroid therapy, alcohol use, HIV, blood dyscrasias, chemotherapy, radiation therapy, age >40 years, and increased BMI (>24 kg/m²) 1
• Avascular necrosis is often bilateral in nontraumatic cases (70-80%), requiring evaluation of both hips 1

Treatment Algorithm Based on Disease Stage

Early-Stage Disease (Pre-Collapse, ARCO Stages 0-II)

1. Core Decompression

   • First-line surgical intervention for early-stage disease 1, 2
   • Success rates: 84% for Stage I and 63% for Stage II 3
   • Significantly more effective than conservative treatment for Stage I hips 3
   • Can be supplemented with:
     • Injection of autologous bone marrow cells 1
     • Vascular fibular grafting 1
     • Electric stimulation 1

2. Pharmacological Options (limited supporting evidence)

   • Bisphosphonates may be efficient in early stages, but no clear recommendations on dosage or treatment duration exist 4
   • Low molecular weight heparin may lower disease progression in idiopathic AVN, but evidence quality is very low 4
   • Statins and vasodilators have very low supporting evidence and cannot be recommended 4
   • Iloprost (PGI2) has shown promising results for ARCO stages 1-2, with significant improvement in subjective complaints and pain scores 5

3. Other Conservative Approaches

   • Weight-bearing restriction alone is insufficient but may be useful when combined with pharmacological agents or surgery 4
   • Extracorporeal shock wave therapy may improve pain and function in early stages but doesn't significantly prevent femoral head collapse 4
   • Hyperbaric oxygen therapy has limited evidence and availability concerns 4

Late-Stage Disease (Post-Collapse, ARCO Stages III-IV)

1. Total Hip Arthroplasty

   • Recommended by the American College of Radiology for late-stage femoral head osteonecrosis with articular collapse 1
   • Provides more consistent, durable, and better results than other options for advanced disease 6
   • For ARCO stage 3,71% of joints required total joint replacement despite conservative treatment; for ARCO stage 4,100% required replacement 5

2. Resurfacing Hemiarthroplasty

   • Alternative to total hip arthroplasty for late-stage disease 1

Surgical Planning Considerations

• CT imaging is essential for surgical planning, showing the precise location and extent of the necrotic lesion 2
• 3D-printed guide plates can improve surgical precision and decrease operative time for core decompression procedures 2, 7
• Protected weight-bearing is recommended following core decompression to prevent fracture 2, 7
• Regular radiographic follow-up is essential to monitor for disease progression or femoral head collapse 2, 7

Special Considerations

• Early diagnosis is crucial to prevent articular collapse and the need for joint replacement 1
• Nontraumatic AVN occurs primarily in younger adults and is often bilateral, making joint preservation particularly important 6
• For traumatic AVN (most commonly from displaced subcapital or transcervical fractures) in elderly patients, endoprosthetic replacement or total hip replacement is typically the treatment of choice 6
• Multifocal osteonecrosis can occur, potentially affecting the knee, ankle, and shoulder 1