An 80-year-old woman presented with low back pain and underwent an MRI of her lumbar spine. The MRI images showed marked signal hyperintensity in the sacrum bilaterally, consistent with edema. Additionally, T1 and T2-weighted images showed hypointensity and linear low signal areas in the sacral alae, consistent with a sacral insufficiency fracture. No tumor, disc herniation, or other abnormalities were observed that could explain her back pain other than the insufficiency fracture.

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2. Our appreciation is extended to Drs. Robert W. Morris,
Steve Kim, and David Pitre, University of Mississippi
Medical Center in Jackson, Mississippi, U.S., for
contributing this case

4. An 80-year-old woman presented for MRI of the lumbar spine to evaluate low-back pain.
Sagittal short-tau inversion-recovery (STIR) images are shown from left to right.

5. There is marked STIR signal hyperintensity in the
sacrum to the left and right of midline, compatible
with edema. There is no disk herniation or tumor on
these images. The conus terminates normally at L1-2,
with no evidence of tethered cord.

6. Axial T1- and T2-
weighted images
from the same
lumbar spine MRI are
shown.

8. The T1 signal hypointensity and linear low signal areas
on the T2-weighted images in the sacral alae are
consistent with a sacral insufficiency fracture. There is
no mass to suggest a chordoma, and there are no
changes along the iliac sides of the sacroiliac joints to
indicate sacroiliitis. The sacral nerve root appears
normal.

9. STIR image of the more caudal sacrum
The axial STIR image obtained at a
more caudal level confirms the
marked edema.

10. Differential diagnosis
Sacral insufficiency fracture
Traumatic sacral fracture
Metastasis
Radiation osteonecrosis
Diagnosis: Sacral insufficiency fracture