Osteonecrosis

Abstract

Osteonecrosis is characterized by the death of cellular components of the bone that results from an interruption of the subchondral blood supply. Bone infarction and avascular necrosis are terms that may be used interchangeably. The risk factors of osteonecrosis are generally multifactorial, such as serious trauma, steroid medication, and alcohol consumption, but the etiology and pathogenesis remain unclear. The common sites for osteonecrosis are the femoral head, knee, talus, and humeral head. Osteonecrosis may lead to subchondral collapse, which threatens the viability of the involved joint. Therefore, early diagnosis is essential since it allows for the treatment of osteonecrosis and potentially improves the outcome.

Initial evaluation is conducted by plain radiographs demonstrating minimal osteopenia followed by variable changes, but it often appears normal in the early stages of the disease. In this regard, bone scintigraphy and MRI are preferred for the diagnosis of osteonecrosis at an earlier stage. MRI is the most sensitive diagnostic modality based on the high spatial resolution for the soft tissue as well as bone, and bone scintigraphy is quite sensitive and advantageous, allowing evaluation of multiple sites of the body. It is expected that bone SPECT/CT can improve the diagnostic accuracy of the evaluation of osteonecrosis, using the functional information of the SPECT images combined with the exact localization information of the CT images.