Bone Scan Area of Interest Because of poor spatial resolution, low specificity, and the inability to quantify the size of the necrotic lesion, bone scintigraphy is not beneficial for characterization of osteonecrosis. SPECT may improve the accuracy of bone scintigraphy [30,32,33] for detection of osteonecrosis, but its use has not been widely accepted. In addition, few studies suggest that bone scan may be used to screen for multifocal osteonecrosis [34,35]. CT Area of Interest With IV Contrast There is limited evidence to support the use of CT with IV contrast as the next imaging study for clinically suspected osteonecrosis following radiographs. CT Area of Interest Without and With IV Contrast There is limited evidence to support the use of CT without and with IV contrast as the next imaging study for clinically suspected osteonecrosis following radiographs. CT Area of Interest Without IV Contrast CT is less sensitive than bone scintigraphy and MRI for the detection of early osteonecrosis [36]. Once an insufficiency fracture occurs, CT is superior to MRI in showing location and extent of articular collapse [37,38]. CT also shows osseous details of secondary osteoarthritis well. MRI Area of Interest Without and With IV Contrast MRI with dynamic contrast enhancement has been shown to be useful to differentiate osteonecrosis from transient bone marrow edema syndrome and subchondral insufficiency fracture [39]. Transient bone marrow edema shows subchondral spot of marked hyperperfusion (plasma flow), whereas osteonecrosis shows a rim of high plasma flow surrounding a subchondral area without flow [40]. This rim is thought to represent granulation tissue. Higher slope of enhancement and maximum enhancement in epiphysis was seen in transient bone marrow edema than in subchondral fracture. Osteonecrosis showed overall decreased maximal enhancement [41].
Osteonecrosis PCAs. Bone Scan Area of Interest Because of poor spatial resolution, low specificity, and the inability to quantify the size of the necrotic lesion, bone scintigraphy is not beneficial for characterization of osteonecrosis. SPECT may improve the accuracy of bone scintigraphy [30,32,33] for detection of osteonecrosis, but its use has not been widely accepted. In addition, few studies suggest that bone scan may be used to screen for multifocal osteonecrosis [34,35]. CT Area of Interest With IV Contrast There is limited evidence to support the use of CT with IV contrast as the next imaging study for clinically suspected osteonecrosis following radiographs. CT Area of Interest Without and With IV Contrast There is limited evidence to support the use of CT without and with IV contrast as the next imaging study for clinically suspected osteonecrosis following radiographs. CT Area of Interest Without IV Contrast CT is less sensitive than bone scintigraphy and MRI for the detection of early osteonecrosis [36]. Once an insufficiency fracture occurs, CT is superior to MRI in showing location and extent of articular collapse [37,38]. CT also shows osseous details of secondary osteoarthritis well. MRI Area of Interest Without and With IV Contrast MRI with dynamic contrast enhancement has been shown to be useful to differentiate osteonecrosis from transient bone marrow edema syndrome and subchondral insufficiency fracture [39]. Transient bone marrow edema shows subchondral spot of marked hyperperfusion (plasma flow), whereas osteonecrosis shows a rim of high plasma flow surrounding a subchondral area without flow [40]. This rim is thought to represent granulation tissue. Higher slope of enhancement and maximum enhancement in epiphysis was seen in transient bone marrow edema than in subchondral fracture. Osteonecrosis showed overall decreased maximal enhancement [41].