Imaging evaluation of patients with osteonecrosis of the femoral head.

Imaging modalities for the diagnosis of osteonecrosis (ON) of the femoral head have been studied extensively, but there have been few reports strictly addressing radiographic evaluation. The purpose of this report is to examine the use and role of (1) plain radiographs, (2) magnetic resonance imaging (MRI), (3) computerized tomography (CT), (4) bone scanning, and (5) positron emission topography (PET) for the diagnostic evaluation of ON. Plain radiographs are a mainstay in diagnosis but have very low sensitivity for early ON. MRI is the gold standard for diagnostic evaluation but may not identify subchondral fractures on collapse as well as CT scan or tomogram. Bone scanning should not be used for diagnosis due to its low sensitivity. PET scanning does not have a definitive role in diagnosis yet. Future research should focus on the role of new imaging technologies in evaluation.