Odontoid Resorption After Posterior Occipitocervical Fusion in Rheumatoid Basilar Invagination

Background Context: Inflammatory arthritis of the cervical spine is common and begins early after the onset of rheumatoid arthritis. Atlantoaxial instability is the most common pattern followed by cranial settling or basilar invagination, with subaxial subluxation being least common. Vertical migration of the odontoid (basilar invagination) poses an increased risk of sudden death from compression of the brain stem. A combination of transoral decompression and posterior occipitocervical fusion has been described, although a single posterior approach stabilization may suffice and avoid the associated comorbidities with an anterior/posterior surgery in a high-risk rheumatoid patient. Purpose: To report a case of odontoid resorption and cervicomedullary angle improvement after occipitocervical fusion. Study Design: A retrospective case report. Methods: Radiographic analysis. Results: After posterior occipitocervical fusion alone for basilar invagination there was a reduction of cervicomedullary angle to 127 degrees at 3 years follow up. This was improved from an initial 115 degrees through odontoid remodeling. Conclusions: Basilar invagination treated with posterior alone occipitocervical stabilization may suffice in providing stability and long term decompression of the cervicomedullary junction through resorption and remodeling of the odontoid. This case study supports the viability of avoiding a transoral resection for an irreducible severely migrated odontoid.