This condition has been proposed as a syndrome that is associated with osteoporosis (Wilson et al. 1988). These authors reported ten patients with hip or knee pain whose radiographs were either normal or minimally os-teopenic at the diseased site. Bone scintigraphy showed increased tracer uptake, and MRI demonstrated decreased signal intensity on T1-
weighted images and increased signal intensity on T2-weighted images, denoting hyperemia and edema. Clinical symptoms slowly resolved over a period of months and did not recur. In one case, intense uptake in the right femoral head returned to a near-normal state after 8 months. Marrow edema might be a coincidental process, but its association with regional osteoporosis cannot be denied. In essence, edema is a nonspecific response of marrow tissue to a variety of physical stresses or injuries (Moore et al. 1991), and is associated with an increased amount of extracellular water as a result of hyperperfusion (Wilson et al. 1988). Etiologically, bone edema has been related to a number of clinical conditions such as osteoporosis, RSD (Murphy and Totty 1986), and Legg-Calve-Perthes disease (Bleumm et al. 1985). The other likely causes include contusion, infection, and primary or metastatic neoplastic disease (Moore et al. 1991).
Our experience indicates that pinhole scintigraphy is a valuable adjunct to the clinical study of this condition, displaying not only ominous lesions (Fig. 14.16) but also extremely subtle changes, which are radiographically invisible (Fig. 14.17). The tracer accumulated in this condition appears to be divided into two different components: the more intense central
Fig. 14.17A-C Transient osteoporosis of the hip. A Anterior pinhole scintigraph of the painful right hip in a 57-year-old woman shows patchy, intense tracer uptake in the lateral aspect of the femoral neck (arrowhead). B Anteroposterior radiograph shows only equivocal osteopenia in the area in question (?). C T2-weighted coronal MRI reveals high signal intensity with a low-intensity rim in the base of the femoral head, corresponding to the scintigraphically "hot" area (arrowhead). On Tl-weight-ed MRI the signal intensity of the lesion was low, denoting edema (not shown here)
uptake and the less intense peripheral or background uptake. Interestingly, our MRI correlation has indicated that the more intense uptake at the lesional center corresponds to edema that is represented by a bright signal on T2-weighted images while the less intense uptake in the periphery corresponds to extended reaction or the watershed phenomenon (Fig. 14.16).
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