Use of a C1-C2 Facet Spacer to Treat Atlantoaxial Instability and Basilar Invagination Associated with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disease that often affects the craniovertebral junction. RA is associated with atlantoaxial instability and basilar invagination; the detailed presentations vary. Surgical treatment of atlantoaxial instability and basilar invagination caused by RA is challenging due to anatomic complexity and poor bone quality. The prevailing procedure is posterior occipitocervical fixation after transoral decompression or posterior decompression followed by occipitocervical fixation. However, these surgical modalities inevitably severely limit neck motion and cause dysesthesia of the C2 dermatome.We report our surgical experience with a C1-C2 facet spacer, specifically the usual cervical cage containing an autologous bone chip combined with a C1 lateral mass screw and a C2 pedicle without resection of C2 roots. The facet space was maintained on the 3-year follow-up radiograph.This method effectively reduces BI and allows AAI fixation without significantly compromising neck motion or causing C2 dermatome dysesthesia.