[Sacred sacrum!].

Post-fracture osteolysis of the sacrum is a rare radiological entity mimicking a serious disease. We report the case of a female patient lost to follow-up after biopsy indication. She presented again after 4 months. During multi-stage bone registration prior to the biopsy, we noticed a change in the appearance of the lesion, associating a linear image (corresponding to the fracture line) with condensation at the edges. Patient's evolution was good after a period of rest at 6-months follow-up. This study highlights the atypical imaging appearance and the diagnostic difficulties associated with post-fracture osteolysis of the sacrum. The particularity of our patient is that symptoms were masked by disc-related nerve root impingement with right L5 root and that the sacrum osteolysis was unexpectedly discovered on CT scan.