Clinical and Radiographic Outcomes of Atlantoaxial or Occipitocervical Fixation and Fusion in Patients With Cervical Myelopathy due to Idiopathic Retro-Odontoid Pseudotumor.

Abstract

Background and objective: A retro-odontoid pseudotumor (ROP) is commonly associated with atlantoaxial dislocation and rheumatoid arthritis in the craniovertebral junction. The formation of ROP without rheumatoid arthritis and atlantoaxial dislocation represents an extremely rare condition known as idiopathic retro-odontoid pseudotumor (IROP). The objective of this study is to investigate the pathogenesis of IROP subsequent to long-segment subaxial cervical spine fusion and assess the efficacy of atlantoaxial or occipitocervical fixation and fusion surgery in its management.

Methods: The characteristics of the patients, surgical strategies, complications, and prognosis were meticulously documented during a retrospective chart review conducted on 8 patients diagnosed with IROP who underwent posterior atlantoaxial or occipitocervical fixation and fusion procedures. The average follow-up period lasted for 20.38 ± 5.93 months, during which neurological function was evaluated using the Japanese Orthopedic Association score and pre- and postoperative MRI imaging measurements were used to assess the regression of IROP by examining retro-odontoid soft tissue maximum thickness. The pseudotumor regression rate was also calculated.

Results: The final follow-up showed that patients who underwent atlantoaxial or occipitocervical fusion without C1 laminectomy achieved regression of IROP. No perioperative complications associated with the surgery were observed, and the neurological function, as indicated by the Japanese Orthopedic Association score, significantly improved.

Conclusion: The formation of IROP is closely associated with the decrease in range of motion of cervical spine following long-segment fixation and fusion of subaxial cervical spine, as well as the increase in biomechanical stress, hyperplasia, and hypertrophy of the ligament around the odontoid process in the upper cervical spine. Following fixation and fusion of the upper cervical spine, IROP can spontaneously regress upon elimination of pathogenic factors. For such patients, C1 laminectomy is unnecessary, and preserving it serves to provide a bone graft bed for upper cervical spine bone fusion.