Early detction of avascular necrosis of the femoral head by 99m technetium diphosphonate bone scan: a preliminary report.

Since roentgenographic changes characteristic of avascular necrosis of the femoral head frequently do not appear for several months after onset of symptoms, it may be difficult to diagnose this condition in its early stages and then institute therapeutic measures designed to prevent collapse of the femoral head and to enhance repair. Bone scans made after intravenous injection of 99mTc DP revealed increased activity over the femoral head in 5 patients with avascular necrosis 2 to 5 months before changes appeared on conventional roentgenograms. Although increased activity at the site of the lesion is not specific for avascular necrosis, the correct diagnosis can usually be established by taking into account other clinical, roentegenographic, and laboratory findings. Bone scanning with 99mTc DP is safe, even for high-risk patients, and relatively simple to perform.