What causes Osteonecrosis?
The etiology of Osteonecrosis is most obvious and best understood in posttraumatic disruption of the arterial blood supply. Fractures of the femoral neck have been associated with ON in 15% of nondisplaced and 25% to 50% of displaced fractures. Hip dislocation causes ON in 10% to 25% of cases.
In Osteonecrosis cases that develop in the absence of trauma, various pathologic processes are capable of inducing hemostasis and, in turn, ischemia. Potential mechanisms include:
• Occlusion of blood vessels from sickled red blood cells, thrombophilia/coagulation disorders, and fat emboli (long bone fractures, fatty liver, hyperlipidemia)
• Bone marrow hypertrophy/infiltration and increased pressure in the bony compartment that compromises blood flow can occur in Gaucher’s, leukemia, myeloproliferative disorders, and corticosteroids (fat hypertrophy)
• Bone marrow cellular toxicity and death because of external factors such as radiation, chemotherapy, and thermal injury.