Causes of Femoral Bone Infarction (Avascular Necrosis)
Femoral bone infarction results from disruption of blood supply to the proximal femur, caused by either traumatic injury or a wide range of non-traumatic risk factors, with corticosteroid therapy and alcohol abuse being the most common non-traumatic causes. 1
Traumatic Causes
- Femoral neck fractures, particularly displaced fractures, are a major traumatic cause of AVN due to disruption of the capsular blood supply to the femoral head 2, 3
- Hip dislocation and associated surgical procedures frequently lead to AVN development 3
- Direct hip trauma compromises vascular supply and increases AVN risk 1
- The type of fracture (displaced versus undisplaced) and time between injury and surgery are the most critical factors in assessing the risk of developing post-traumatic AVN 3
Non-Traumatic Causes: Medication-Related
- Corticosteroid therapy is identified as one of the most common causes of hip osteonecrosis 1
- Daily prednisolone doses of ≥30 mg markedly increase the risk of developing AVN, especially when the dose is escalated rapidly without prior tapering 1
- Chemotherapy is a recognized risk factor for hip osteonecrosis 1
- Radiation therapy can lead to AVN of the femoral head 1
Non-Traumatic Causes: Substance Use
- Alcohol consumption is a major risk factor and one of the most frequent causes of non-traumatic AVN 1, 3
- Chronic alcohol abuse disrupts blood supply to the proximal femur 3
Non-Traumatic Causes: Hematologic and Metabolic Disorders
- Hemoglobinopathies, including sickle cell disease, are well-established causes of bone infarction 1, 4
- Hypercoagulable states increase the risk of AVN through thrombotic mechanisms 1
- Gaucher disease is a recognized metabolic cause of femoral head osteonecrosis 1
- Hyperlipidemia contributes to AVN risk 1
Non-Traumatic Causes: Infectious and Systemic Diseases
- HIV infection is a significant risk factor for hip osteonecrosis 1
- Lymphoma and leukemia are associated with increased AVN risk 1
- Pancreatitis can result in avascular necrosis of bone 5
- Liver cirrhosis is associated with bone infarcts 4
Non-Traumatic Causes: Occupational and Environmental
- Caisson disease (decompression sickness) from rapid changes in atmospheric pressure causes AVN 1
- Prolonged standing or mechanical stress may contribute to AVN development in certain cases 4
Non-Traumatic Causes: Idiopathic
- A significant proportion of AVN cases have unclear (idiopathic) etiology where no specific cause can be identified 6
Underlying Pathophysiologic Mechanisms
- The pathogenesis involves five main mechanisms: hypercoagulable conditions, angiogenesis suppression, hyperadipogenesis, heritable states, and switching bone remodeling into bone resorption 7
- Elevated homocysteine levels and reduced vitamins B6 and B12 have been demonstrated in AVNFH patients, suggesting a metabolic component 6
- All pathogenic factors ultimately lead to anoxic death of bone cells caused by interrupted blood supply 4, 3
Critical Clinical Considerations
- Nontraumatic osteonecrosis is bilateral in 70-80% of cases, requiring evaluation of both hips even when symptoms are unilateral 1
- Multifocal joint involvement is common in non-traumatic AVN: the knee is affected in approximately 44%, the ankle in 17%, and the shoulder in 15% of cases 8
- Prolonged dialysis prior to renal transplantation increases the probability of developing AVN 1