Malunion in a Self-stabilized Fracture of the Odontoid Process Type II with a Chronic Anterior Atlantoaxial Subluxation in a Neurologically Intact Patient: A Case Report.

Atalanto-occipital dislocations with type II fractures of the odontoid process are rare, reporting 7 cases for every 784 upper cervical spine injuries, an incidence of <0.3% and are related to a high rate of morbidity and mortality. Regarding C2 fractures, the most common are in the odontoid process, representing 7%, classified by Anderson and D'Alonso according to their level, with the highest rate of pseudarthrosis in zone II of up to 85% are caused mainly by car accidents. In the acute event, there is no consensus regarding its optimal management. We performed a complete anamnesis and a physical examination in our institution. A systematic review of case reports was carried out with the keywords "mal-union, type II odontoid process fracture, chronic atlantoaxial subluxation" in four different databases, and a comparative analysis of the cases found was performed. There were not found identical cases to the one in our report, 9 similar case reports were published with the general differences of a pseudarthrosis of the odontoid process, as well as neurological alterations in symptomatic patients and the consequent surgical treatment. Observing a patient with a type II odontoid process fracture consolidating viciously and a stable anterior atlantoaxial subluxation without neurological alterations is rare. We determined to maintain expectant management with annual follow-up.