[Os odontoideum. Etiology, clinical aspects, therapy]

The etiology of os odontoideum is still controversial. In most patients, it is found by accident because of neurological symptoms and/or painful range of motion of the cervical spine. Upon recognition of the os odontoideum, it is unknown whether or not immediate surgery is beneficial. This is in contrast to an "unstable" os odontoideum, which could result in atlantoaxial instability or compression of the myelon. In this study, we present the results of our treatment of four patients with an unstable os odontoideum. In all four cases, a C1-2 fusion was performed (3 x Magerl/Seemann, 1 GallieBrooks). Postoperatively, we found a complete regression of neurological symptoms in three patients and one was significantly improved. The range of motion of the cervical spine was free of pain in all patients. As a result, we strongly support immediate surgical treatment of an unstable os odontoideum in order to prevent severe and life-threatening neurological complications.