Avascular Necrosis (AVN), sometimes referred to as Aseptic Necrosis or Osteonecrosis, is an area of bone death resulting from poor blood supply to that bone. Dead areas of bone do not function normally, can eventually become weakened and collapse. The femoral head of the hip joint is a bone known to be prone to AVN.
Causes of AVN include trauma to the hip with subsequent damage to the blood vessels that supply the bone oxygen. Blockage of a bone’s blood supply by air or fat, abnormal blood vessel inflammation or unusually thick blood, are other known causes of AVN.
A variety of conditions are associated with AVN. Among these are alcoholism, corticosteroid medications, sickle cell anemia, Lupus, and radiation exposure.
AVN of the hip initially starts as a painless bone condition. Later, as the disease progresses and the bone weakens, pain develops, especially with weight bearing activities. Pain in the groin region can be felt with hip rotation when bone collapse progresses, eventually leading to pain at rest.
Diagnosis of AVN can be made from imaging studies. In the early phases of the disease, AVN may only be visualized by MRI. As the disease advances, changes become apparent on plain X-rays and signify a more advanced stage of the disease.
The treatment of AVN is highly dependent on the stage of the disease at the time of diagnosis. Early treatment may involve a procedure termed core decompression, where a core of bone from the involved area is drilled out and sometimes grafted with new bone. This is thought to allow a new blood supply to form with the goal of preserving the remaining bone. In later stages of the disease, significant changes to the bone and surrounding joint may require a joint replacement for treatment.