Lumbosacral fracture-dislocation is a rare occurrence. There are more than 73 cases reported in the English literature. We report on the imaging findings and surgical treatment in a patient suffered of unilateral traumatic L5-S1 dislocation associated with severe disruption of the posterior ligamentous complex. The patient underwent open reduction and stabilization of L4-S1 vertebrae with posterior instrumentation system. Open reduction and internal fixation was mandatory as post-traumatic ligamentous insufficiency would lead to abnormal motion. Operative treatment managed to produce a solid arthrodesis and restore stability of the lumbosacral junction. Follow-up revealed excellent results. This study reports a rare injury of the lumbosacral junction, and the literature concerning this unusual condition is extensively reviewed.