Osteonecrosis of the femoral head (ONFH) is a disabling condition that affects mainly younger subjects, in the midst of their working lives; to this day, it has remained a devastating disease. Its treatment stands at the borderline between Medicine and Surgery, and requires a thorough understanding of the pathogenesis, the natural history, and the treatment options as a function of the different disease stages, which are best assessed with further investigations.
Osteonecrosis (ON) may be defined as the death of the cell components of bone - both osteocytes and bone marrow cells. ONFH is not a specific entity, but the final common pathway of various conditions that impair the blood supply to the femoral head - hence the frequently used term avascular necrosis.
Osteonecrosis (ON) may be defined as the death of the cell components of bone - both osteocytes and bone marrow cells. ONFH is not a specific entity, but the final common pathway of various conditions that impair the blood supply to the femoral head - hence the frequently used term avascular necrosis.
MRI Imaging revealed:
ONFH most commonly involves the anterosuperior portion of the femoral head. An MRI scan of a normal femoral head will show a uniformly high signal intensity on T1- and T2-weighting, throughout the femoral head. In the overwhelming majority of cases, the basic pattern of ON consists in a zone of decreased signal intensity on T1- and T2-weighted images. This low-intensity zone is at the site shown as a necrotic region on plain radiographs, in typical osteonecrosis with femoral head collapse. The low-intensity zone may be homogeneous or heterogeneous, with a speckling of high intensity against the low-intensity background, both on T1- and on T2-weighted images.
Early on, the most typical image is a thin low-intensity band on T1- and T2-weighting, which goes to the subchondral bone and is more or less concave towards the top of the femoral head.
With gadolinium, the contrast of the marrow spaces is enhanced, and the sensitivity of the technique for the detection of ON is improved. Gadolinium contrast enhancement may also be useful in screening for femoral head perfusion problems after hip fractures.
Early on, the most typical image is a thin low-intensity band on T1- and T2-weighting, which goes to the subchondral bone and is more or less concave towards the top of the femoral head.
With gadolinium, the contrast of the marrow spaces is enhanced, and the sensitivity of the technique for the detection of ON is improved. Gadolinium contrast enhancement may also be useful in screening for femoral head perfusion problems after hip fractures.
MRI pattern of a small incipient ONFH lesion. A.p. and lateral views. The zone inside the necrotic segment is still of high intensity.
Avascular necrosis of the femoral head
Avascular necrosis of the capitate
Avascular necrosis of the femur
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