What is the treatment for Avascular Necrosis (AVN)?

Treatment for Avascular Necrosis (AVN)

Treatment for avascular necrosis should be stage-based, with early intervention before subchondral collapse significantly improving outcomes. 1

Diagnosis and Staging

• MRI is the gold standard for diagnosis and staging of AVN
• The Ficat and Arlet classification is most commonly used for femoral head AVN:
  • Stage I-II: Pre-collapse (early stages)
  • Stage III-IV: Post-collapse (advanced stages)
• Necrotic volume assessment is critical:
  • ≥30% necrotic volume: 46-83% risk of collapse
  • <30% necrotic volume: <5% risk of collapse 1

Treatment Algorithm

Early Stage AVN (Pre-collapse: Ficat and Arlet Stage I-II)

1. Conservative Management:

   • Address modifiable risk factors:
     • Reduce/discontinue corticosteroids if possible
     • Manage hyperlipidemia (consider statins)
     • Eliminate alcohol consumption 1
   • Pharmacological therapy:
     • Bisphosphonates to improve bone density and prevent progression (with calcium and vitamin D supplementation) 1
     • Adequate pain management:
       • First-line: Regular acetaminophen and cautious use of NSAIDs
       • Second-line: Opioids for severe pain (reduced dosing in renal dysfunction) 1

2. Surgical Interventions:

   • Core decompression (primary surgical option) 1, 2
     • Can be supplemented with:
       • Autologous bone marrow cell injection
       • Bone substitute filling
       • Tensor fascia lata muscle pedicle bone graft (83.07% satisfactory outcomes in stage IIA, IIB, and III) 2
   • Vascular fibular grafting
   • Electric stimulation 1

Advanced Stage AVN (Post-collapse: Ficat and Arlet Stage III-IV)

1. Total Joint Replacement:

   • Primary treatment for advanced stages with articular collapse
   • Accounts for 10% of total hip replacements in the US 1

2. Alternative Surgical Options:

   • Resurfacing hemiarthroplasty for femoral or humeral head AVN with articular collapse
   • For talar AVN: Talar resection/replacement with arthroplasty or tibiotalar joint fusion 1, 3
   • Total talar replacement (TTR) for talar AVN offers advantages over joint-sacrificing procedures:
     • Avoids delayed union
     • Prevents limb shortening
     • Maintains mobility
     • Prevents stiffening of adjacent joints 3

Special Considerations

AVN in Specific Populations

1. HIV-infected patients:

   • Will ultimately require hip replacement if symptomatic
   • Routine radiographic monitoring not recommended in asymptomatic persons
   • Consider bisphosphonate therapy if bone densitometry shows osteopenia 1

2. Post-transplant patients:

   • Higher risk with longer duration of pre-transplant dialysis
   • Risk increases with higher glucocorticoid dosage 4
   • Low-dose glucocorticoid regimens reduce AVN risk compared to high-dose regimens 4

3. Pediatric oncology patients:

   • Core decompression with bone substitute filling can be effective 5
   • Monitor closely during steroid and cytostatic treatment for leukemia, lymphoma, and other cancers 5

Rehabilitation

• Physical therapy and gentle mobilization once acute pain subsides
• Focus on restoring normal gait and function 1

Emerging Therapies

• Mesenchymal stem cell-based treatments show promise for improving functional prognosis, particularly in early stages 6
• 3D-printing technology is advancing total talar replacement options for talar AVN 3

Pitfalls and Caveats

1. Delay in diagnosis can lead to irreversible joint damage - maintain high index of suspicion in at-risk patients
2. Failure to assess necrotic volume can lead to inappropriate treatment selection
3. Neglecting modifiable risk factors can lead to disease progression despite treatment
4. When using bisphosphonates, calcium and vitamin D supplementation is essential
5. In patients with renal dysfunction, NSAIDs and certain opioids should be used with caution