Management of Avascular Necrosis of the Femoral Head

Abstract

Osteonecrosis of the hip is a disease that generally affects patients in the third to fifth decades of life and therefore has significant impact on the work and leisure activities of these patients. The femoral head is the most vulnerable site for development of osteonecrosis. The site of necrosis is usually immediately below the weightbearing articular surface of the bone, the anterolateral aspect of the femoral head. This is the site of greatest mechanical stress. The head of the femur is entirely intracapsular, and therefore the blood supply of the head is of surgical importance. Around the neck, at the attachment of the fibrous capsule of the hip joint, is a vascular ring supplied by the branches of the medial and lateral circumflex arteries. Osteonecrosis seems to develop as a result of a multifactorial process rather than one precipitating event. Certain patients probably are predisposed to having osteonecrosis develop because of an inherent hypercoagulable state. Patients who are taking corticosteroids clearly are at risk for having osteonecrosis develop. Especial attension should be directed to patients who have any of the risk factors and negative radiograph findings. This is especially true with unilateral involvement because of the high risk of developing osteonecrosis in the contralateral hip. These patients should be evaluated aggressively. The etiology of osteonecrosis of the hip may have a genetic basis. The interaction between certain risk factors and a genetic predisposition may determine whether this disease will develop in a particular individual. The most likely final pathogenic pathway for nontraumatic osteonecrosis involves intravascular coagulation and microcirculatory thrombotic occlusion. Efforts are being made to identify individuals with a heritable tendency to intravascular coagulation who may be at risk for osteonecrosis Understanding the pathogenesis of osteonecrosis is likely to have significant impact upon treatment. The ultimate goal of treatment of a patient with osteonecrosis of the hip is preservation of the femoral head. Preservation of the femoral head is possible only in the early stages of osteonecrosis, before subchondral fracture and collapse.