Diagnosis of Circulatory Disorders

Osteonecrosis is a common condition that is believed to develop after an ischemic event in the bone and bone marrow and is likely due to intravascular coagulopathy. It may be secondary to many other known causes, such as trauma, sickle cell disease, and steroid intake. It may also be primary, or idiopathic, with no apparent cause such as Legg-Calvé-Perthes disease in the pediatric age group and spontaneous osteonecrosis of the femoral head and knee in adults. Bone scintigraphy is more sensitive than standard radiographs, while MRI is an excellent complementary modality. Generally, early on, bone scanning shows decreased activity with a subsequent progressive increase in uptake, which starts at the periphery. SPECT is more sensitive than planar imaging, and pinhole imaging is particularly useful in children and small bones. Osteonecrosis may affect one bone or can be multifocal. The osteochondroses are a group of conditions mostly affecting children and adolescents that are characterized by the alteration of endochondral ossification; some forms feature osteonecrosis, such as Freiberg’s disease (affecting the second metatarsal head), Kohler’s disease (affecting the navicular bone and occasionally the patella), and Osgood-Schlatter disease (affecting the tibial tuberosity).