Cause

The emergence of this serious bone condition among people with HIV so many years into the HIV/AIDS epidemic is puzzling. NIH researchers have postulated several factors which may contribute to osteonecrosis including longer survival of people with HIV, treatments and therapies, or lifestyle factors.

The NIH study did provide some clues about the cause of osteonecrosis. Those with the condition were more likely to have taken testosterone, lipid-lowering drugs and corticosteroids, which may be taken for HIV-related conditions or metabolic disorders associated with antiretroviral therapy. The individuals also were more likely to have done weight training or body building. Osteonecrosis was not associated with immunodeficiency or any pattern of antiretroviral usage. However, recent studies have shown an association between length of exposure to highly active antiretroviral therapy (HAART) and osteonecrosis,¹ and with a previous AIDS-defining illness or previous CD4 cell count below 200 cells/mm³.²

Another study has linked aseptic bone necrosis in HIV-infected men to the use of the synthetic hormone megestrol acetate, which is used to treat AIDS wasting.³ Further research is required to identify the risk factors for this disease in HIV-positive people.

In non-HIV-infected populations, osteonecrosis is associated with alcoholism, steroid usage, pancreatitis, radiation exposure and various hormonal diseases. It can be caused by trauma or damage to the blood vessels that supply bone with oxygen or by a blockage in the bloodstream due to fat or an air bubble, very thick blood or inflammation of the blood vessels.