ISCHEMIC necrosis (avascular necrosis, osteonecrosis) may occur in almost any bone of the skeleton. The most common site for ischemic necrosis is the head of the femur, and it is here that early diagnosis has proved to be most difficult. The patient often complains of pain, sometimes during a period of several months before any specific radiological findings become visible. It is possible to make the diagnosis earlier if clinical suspicion is high and certain specific roentgenograms are obtained. Many centers are using radioisotopes in an attempt to demonstrate changes before those observed radiologically. Although the computed tomographic (CT) scanner is an excellent method for confirming advanced disease, so far it has not proved useful in the diagnosis of early ischemic necrosis.
The Etiology of Ischemic Necrosis
The causes of osteonecrosis may be subdivided into three categories: posttraumatic (the most common), nontraumatic (including embolic small-vessel disease and abnormal deposition of