Microscopic decompression of the anterior upper cervical spine: a case of odontoid malunion to the atlas.

For the past 20 years, the transoral approach to the upper cervical spine has been utilized for odontoid fractures, the removal of an abnormal odontoid process, decompression of basilar impression, and biopsy or resection of nasopharyngeal or metastatic tumors. The effectiveness and safety of this procedure is well documented. Use of the surgical microscope adds to the efficiency and safety of the procedure. We are reporting a case of fusion of the odontoid base to the anterior arch of the atlas. To our knowledge, this entity has not been described previously. The spinal cord was protected by an initial posterior fusion of C-1, C-2, followed in 10 days by a tracheostomy and the transoral removal of the anterior C-1 arch and the abnormal dens. Because the medical history did not reveal a source of trauma, it is supposed that the patient had malunion of the odontoid process to C-2, with subsequent migration and fusion of the dens to the C-1 arch.