What are the risk factors for avascular necrosis?

Risk Factors for Avascular Necrosis

The primary risk factors for avascular necrosis (AVN) include corticosteroid therapy, alcohol use, trauma, HIV infection, lymphoma/leukemia, blood dyscrasias, chemotherapy, radiation therapy, Gaucher disease, and Caisson disease. 1

Common Risk Factors

Avascular necrosis, also known as osteonecrosis, is defined as bone death due to inadequate vascular supply. It most commonly affects adults in their third to fifth decades of life. The major risk factors can be categorized as follows:

Medication-Related

• Corticosteroid use: One of the most significant risk factors, with higher doses associated with greater risk 1
  • Meta-analysis shows high-dose glucocorticoids result in significantly more cases of AVN than low-dose regimens (1.5-fold greater risk) 1
• Immunosuppressive therapy in transplant patients 1, 2

Lifestyle Factors

• Alcohol abuse 1, 3, 4
• Hyperlipidemia/hypercholesterolemia 2, 3

Medical Conditions

• Sickle cell disease: Causes vaso-occlusion leading to osteonecrosis, particularly affecting femoral and humeral heads 5
• HIV infection 1, 2
• Systemic lupus erythematosus 4
• Blood dyscrasias including lymphoma and leukemia 1
• Gaucher disease 1

Trauma-Related

• Fractures, particularly displaced femoral neck fractures 6
• Hip dislocations 6
• Prior surgical procedures on the affected area 6

Environmental Factors

• Caisson disease (decompression sickness) 1
• Radiation therapy 1

Special Considerations

Transplant Patients

Patients who have undergone kidney transplantation are at particular risk for AVN. Risk factors in this population include:

• Duration of dialysis prior to transplantation (longer duration increases risk) 1
• Glucocorticoid dosage (higher doses increase risk) 1
• Immunosuppressive regimen 1

Multifocal AVN

AVN can be unifocal or multifocal, with the latter suggesting a systemic origin 3. Common sites include:

• Femoral head (>75% of cases) 3
• Humeral head 4
• Knee 2
• Ankle 2
• Scaphoid and lunate bones 1
• Talus 1

When AVN is diagnosed at one site, screening for AVN at other sites should be considered, particularly in patients on steroids 2.

Clinical Implications

Early identification of risk factors is crucial as:

1. Early diagnosis allows for possible surgical prevention to prevent articular collapse and need for joint replacements 1
2. AVN accounts for approximately 10% of total hip replacements in the US 2
3. Modifiable risk factors (corticosteroid use, hyperlipidemia, alcohol consumption) should be addressed when possible 2

Monitoring High-Risk Patients

For patients with significant risk factors:

• MRI is the gold standard for early diagnosis, even when X-rays appear normal 2
• Pain is often the trigger for diagnostic imaging, with location varying based on the affected site 2
• In asymptomatic patients with risk factors (particularly those on steroids or with sickle cell disease), consider periodic screening 2, 5

Understanding these risk factors is essential for early identification and intervention in avascular necrosis, potentially preventing progression to joint collapse and the need for joint replacement.