Introduction: Isolated fractures of the sacrum are rare and in principle related to a direct posterior shock. The occurrence of a pseudarthrosis of a sacrum associated with neurological disorders is an exceptional eventuality.Case: Female subject 38, victim of a traffic accident occurring 3 months previously, consulted for a neglected trauma of the left hemi pelvis with relative functional impotence of the lower left limb. Clinical examination resulted in a painful lameness with a makeshift cane, pain in inguinal palpation and mobilization of the left hip. The gluteus medius muscle was rated at 0. There were no sphincteric disorders.Observations: The standard X-ray showed a fracture of the left ischiopubic branch. At CT, there was also a vertical fracture of the left hemi-sacrum passing through the sacral holes and a fracture of the anterior column of the homolateral acetabulum.The electromyogram showed a left L5 and S1 radiculopathy, a truncular involvement of the SPI (myelinic type) and of the left SPE (axonal type).At 6 months of follow-up and after a medico-physical treatment (analgesic of pallium-II, vitamino-therapy B and functional rehabilitation); the patient fully recovered with pain only squatting and a gluteus medius to 5. Results and Conclusion:In traumatology of the pelvis, the standard images are often ill-readable, hence the interest of CT. In the absence of displacement and / or root compression, functional treatment is mandatory. The occurrence of a pseudarthrosis associated or not with irreducibility or a persistence of the neurological syndrome indicates a surgical approach.