Objective To explore the 18F-FDG PET/CT features of sacral insufficiency fracture.Methods 18 F-FDG PET/CT imaging and clinical data of 8 patients with sacral insufficiency fracture were retrospectively analyzed.Results All 8 patients had different degrees of radioactivity uptake in sacra with the maximum standardized uptake value (SUVmax)from 2.7 to 7.2.Four patients had lesions in their left sacra,2 in the bilateral sacral wings and sacral promontories,1 in the bilateral sacral wings,and 1 in the left sacral wing and sacral promontory.There were 8 patients of longitudinal fractures in sacral wings,which of 6 patients involving S1-2 and 2 patients involving S3.Three patients had transverse fractures in sacral promontories,with 2 located at S2 and 1 at S3.The sacral bone density increased in 5 cases,and the density was not changed in 3 cases.Conclusion Sacral insufficiency fracture had specific 18F-FDG PET/CT characteristics.