Marrow infarction in sickle cell anemia: correlation with marrow type and distribution by MRI.

Ischemic necrosis of bone is believed to occur exclusively in areas of predominantly fatty marrow. Sickle cell disease is unusual in that marrow infarction occurs in areas of active hematopoiesis. MR images of long bone obtained in ten patients with sickle cell anemia (SCA) were analyzed to correlate the distribution and appearance of marrow infarction with the type of marrow. While the hematopoietic marrow predominated in metaphyseal and diaphyseal regions of femurs and tibias, the fatty or mixed marrow was the most common pattern in epiphyses. Infarcts occurred in fatty as well as hematopoietic marrow. Marrow infarcts were isointense or minimally hyperintense on T1 weighted images with the hematopoietic marrow and therefore difficult to detect. On T2 weighted images, the infarcts showed very high signal. T2 weighted images are essential for detection of marrow infarction. Soft tissue changes seen as low signal on T1 and high signal on T2, may be secondary to intramuscular injections of analgesics or muscle ischemia occurring during sickle crisis.