Idiopathic bone necrosis of the femoral head. Early diagnosis and treatment.

Our understanding of idiopathic necrosis of the femoral head depends upon two fundamental concepts. The first is that a standard radiograph shows only the shadow of the mineralised portion of a bone. The radiographic appearance of living bone is the same as that of dead bone ofEgyptian mummies or prehistoric skeletons. Consequently, bone necrosis has no specific radiographic appearance and a normal radiograph does not necessarily mean a normal hip. A standard radiograph cannot help with early diagnosis, and every case of bone necrosis must pass through a preradiographic stage. When radiographic changes do appear, they are due to the reaction of living tissue to the ischaemia. The second fundamental concept is that bone necrosis is the end result of severe and prolonged ischaemia. This again presupposes an initial stage in which vascular and medullary abnormality passes undetected by routine radiography. These concepts point the need for other methods of investigation, especially in early cases. These methods include scintimetry and the study of the haemodynamics of the medullary circulation, termed by us the functional exploration of bone (FEB). These methods of diagnosis, together with a classification developed in association with Professor J. Arlet, are now presented (Ficat and Arlet 1977, 1980).