huge ABC of the sacrum, MRI and CT

Hi, dear OCADERS,
Again I need your advice
45 y old male, huge ostelitic lesion of the sacrum, fluid-fluid levels
inside – aneurysmal bone cyst in my opinion. I cannot think of any DD
But:
1. there is an area of modified bone structure, outside the ABC, 1/3 distal
of the right sacrum, near sacroiliac joint, with some …vessels inside,
some enhancement, CT is not that clear. Could it be an area of bone
displasia (associated with ABC) or a haemangioma?? (what would be the
chance?), stress reaction on the remaining bone? or do you have any other
ideas?
2. the ct revealed some calcification on the obturator membrane,
bilaterally. Not familiar with this pattern. Is this from an old
inflammation? sort of entesitis or it some sort of metabolic extraoseus
calcium deposition? Suppose there is no relation with the ABC…

Any answers would be highly appreciated!
thank you,
sorin

45y-old-male.pdf