Higher incidence of delayed bone fusion for atlantoaxial fusion versus occipitocervical fusion with navigation system

Background Due to the high stresses placed on the upper cervical spinal region, achieving firm fixation and solid bony fusion is essential for good surgical outcomes. However, few reports have addressed bony fusion in procedures involving this region. The present investigation evaluated bony union in fusion procedures for surgical treatment of the upper cervical spinal region and searched for factors associated with fusion failure. Methods The medical data of 84 consecutive patients (38 male and 46 female; mean age: 68.7 years) who underwent upper cervical spinal fusion surgery were retrospectively examined. The surgical techniques used were occipitocervical (O-C) fusion in 45 patients and atlantoaxial fusion with trans-articular screws in 39 patients. To determine the incidence of bony union, the cohort was divided into O-C fusion and atlantoaxial fusion groups and examined for the presence of delayed bony union. Logistic regression models were employed to analyze the prevalence, characteristics, and risk factors of delayed bony union. Results Overall, 20.2% of upper cervical spinal fusion surgery patients experienced delayed bony union. In comparisons of the O-C fusion and atlantoaxial fusion groups, we observed no remarkable differences for age, gender, or steroid use, although rheumatoid arthritis was significantly more common in the O-C fusion group (p < 0.001). Bony fusion rates tended to be higher in the O-C fusion group (86.6%) than in the atlantoaxial fusion group (71.7%). Multivariate analysis identified atlantoaxial fusion to be more strongly associated with delayed bony union (odds ratio: 2.6). Conclusion Approximately 20% of patients undergoing upper cervical spinal fusion surgery experienced delayed bony union. With an odds ratio of 2.6, atlantoaxial fusion was strongly related to this complication.