Risk Factors and Clinical Characteristics of Femoral Head Avascular Necrosis

Traumatic Causes

• Femoral neck fractures, particularly displaced fractures, disrupt the capsular blood supply to the femoral head and are a major traumatic cause of avascular necrosis (AVN). 1
• Direct hip trauma compromises vascular supply and increases the risk of developing AVN. 2

Medication‑Related Non‑Traumatic Causes

• Systemic corticosteroid therapy is one of the most common causes of hip osteonecrosis. 2
• High‑dose prednisolone (≥30 mg daily) markedly raises AVN risk, especially when the dose is rapidly escalated without prior tapering. 2
• Chemotherapy is a recognized risk factor for hip osteonecrosis. 2
• Radiation therapy can lead to femoral‑head AVN. 2

Substance‑Use Related Non‑Traumatic Causes

• Alcohol consumption is a major non‑traumatic risk factor and one of the most frequent causes of AVN. 2

Hematologic and Metabolic Disorders

• Hemoglobinopathies (e.g., sickle‑cell disease) are well‑established causes of bone infarction. 2
• Hypercoagulable states increase AVN risk through thrombotic mechanisms. 2
• Gaucher disease is a metabolic disorder associated with femoral‑head osteonecrosis. 2
• Hyperlipidemia contributes to AVN risk. 2

Infectious and Systemic Diseases

• Human immunodeficiency virus (HIV) infection significantly raises the risk of hip osteonecrosis. 2
• Lymphoma and leukemia are associated with an increased incidence of AVN. 2

Occupational and Environmental Factors

• Caisson disease (decompression sickness) resulting from rapid atmospheric pressure changes can cause AVN of the femoral head. 2

Clinical Considerations

• Bilateral involvement occurs in 70–80 % of non‑traumatic AVN cases; therefore, both hips should be evaluated even when symptoms are unilateral. 2
• Multifocal joint involvement is common in non‑traumatic AVN: the knee is affected in ~44 % of cases, the ankle in ~17 %, and the shoulder in ~15 %. 3
• Prolonged dialysis before renal transplantation increases the probability of developing AVN. 2

Prognostic Indicators and Pathophysiology of Femoral Head Necrosis

Pathophysiological Mechanisms

• The disease may arise through three proposed mechanisms—vascular interruption, vascular occlusion, or extravascular intra‑osseous compression—with lipid hypertrophy considered the most likely cause of the latter mechanism【4】.

Imaging‑Based Prognostic Indicators

• Femoral head lesions with a necrotic volume > 30 % progress to sub‑chondral collapse in 46–83 % of cases, whereas lesions with a necrotic volume < 30 % collapse in fewer than 5 % of cases, indicating that necrotic volume is a strong predictor of future joint collapse【4】.