Insufficiency fractures of the sacrum.

Insufficiency stress fractures may occur in the sacrum after radiation therapy or secondary to postmenopausal or steroid-induced osteoporosis. These fractures are often either overlooked or confused both clinically and radiographically with metastatic disease. Findings on plain films and conventional tomograms are often subtle. Radionuclide bone scans show a characteristic distribution of increased uptake. Computed tomography is the definitive technique for demonstrating the fractures.