RESUMEN
INTRODUCTION: Traumatic upper cervical spine injuries are frequently associated with high-energy trauma. The potential injuries to vital organs associated to a possible neurological damage marks the severity of this pathology. The neurological structures can be affected by a primary injury, spinal cord, cranial nerves and spinal nerves; or secondary to a vascular compromise, mainly the vertebral arteries. The dislocation of the atlantoaxial joint causes an unstable cervical spine that could be often associated with fracture of the Atlas and Axis. Evidently, these have a high morbimortality rate. CASE PRESENTATION: A young woman who suffered a severe polytrauma secondary to a motor vehicle collision was diagnosed with a sagittal plane atlantoaxial joint dislocation associated with a type III odontoid fracture, despite an adequate initial polytrauma management, the neurological damage was too critical, ultimately the decease of the patient. DISCUSSION: The atlantoaxial joint dislocation is a rare condition of the upper cervical spine and is usually secondary to a high-energy traumatism. The disruption of the atlantoaxial ligaments originates the considered most unstable cervical spine lesion and with the highest mortality. Attributable to the kinetic the bone fracture of the Atlas and Axis are commonly related, specially the odontoid process. Early immobilization followed by surgical decompression and stabilization is primordial. Typically, these injuries have an ominous prognosis, that is aggravated if added a polytrauma affecting adjacent neurological structures and other vital organs.