U-shaped sacral fractures are uncommon and are mostly the consequence of a high-energy kinetic trauma. The sacrum is a crucial element for sagittal alignment in a standing position as it determines the value of the pelvic incidence, which is a fixed and unchanging parameter for a given individual. We report the case of a 21-year-old man who underwent corrective surgery for a type II U-shaped fracture of the sacrum (according to the Roy-Camille classification), associated with a S1–S2 dislocation and sacral kyphosis that modified the patient's pelvic incidence. At one-year follow-up, radiographic examinations revealed solid bony fusion and stable results after removal of the implants. The surgery was managed for neurological decompression, stabilization of the fracture and correction of sacral kyphosis. The restoration of the theoretical pelvic incidence depended on the estimated lumbar lordosis. The aim of this study was to highlight the particularities in the management of a sacral U-shaped fracture and their relationship with the sagittal alignment.