Scintigraphy in the diagnosis of osteonecrosis.

Scintigraphy, using 99mTc diphosphonate, has the potential for diagnosing osteonecrosis before irreversible changes are visible in routine roentgenograms. If obtained within weeks of an avascular insult, a cold area will appear on scintiscan. However, months later, the revascularization and reparative processes of the dead bone produce a hot area on scintiscan.