Stress Fracture Sacrum -Case Discussion

50 yr old post menopausal lady with back pain. Case submitted by Dr MGK Murthy.

(A)What is the finding?
An ill defined, irregular ,marrow oedema with no joint abnormality with subtle vertical dark line on T2

(B)What is the diagnosis ?
The finding is nonspecific to etiology. The possibilities include
-Bone marrow syndrome -this  is supported by  focal osteoporosis on Xray, however is unusual site for occurrence
 -Insufficiency fracture-possible because of the gender and age ,as well as subtle darkline on T2 and the orientation is vertical .
However there is no horizontal component across the middle of sacrum at S2 or S3 , and the second vertical component of Honda sign
- sacroilitis of non specific cause-  is unlikely as the joint is not abnormal
-sacroilitis of infective variety possibly TB-unlikely as there is no destruction, joint involvement, and no soft  tissue collection

(C) what should be next step?
Radionuclide scan will show Honda sign of  increased activity. CT would show fracture line

(D) what should be done if the patient is not keen get other tests done?
As the treatment is usually conservative ,  Review after treatment for at least 6 weeks is helpful

(E) Is it necessary to do Review MRI?
No , A review Xray  would be adequate , as it is likely to show sclerosis along the fracture line