Radiology, Vol 188, 241-244, Copyright © 1993 by Radiological Society of North America
Radiation-induced insufficiency fractures of the sacrum: evaluation with MR imaging
V Blomlie, HH Lien, T Iversen, M Winderen and K Tvera
Department of Diagnostic Radiology, Norwegian Radium Hospital, Oslo, Norway.
In patients with malignant pelvic tumors, radiation-induced insufficiency
fractures of the sacrum may be mistaken for metastasis. Magnetic resonance
(MR) imaging was performed in 18 patients with this condition, and the
findings were studied retrospectively. The diagnosis was confirmed with at
least one additional imaging modality in 16 patients, whereas the other two
patients underwent clinical follow-up at 13 and 20 months without evidence
of metastasis. In 17 patients, the lesions were consistent with edema and
had diffuse low signal intensity on T1-weighted images and diffuse high
signal intensity on short- inversion-time inversion-recovery images,
thereby simulating metastasis. In one patient, bilateral sacral wing
fractures were demonstrated directly as fairly well-defined linear zones.
The alae sacri were involved in all patients; 16 patients had bilateral
lesions. Awareness of this clinical entity and of the high sensitivity of
MR imaging for demonstrating edema caused by the fracture should prevent
confusion with metastatic disease and inappropriate treatment.
