A RETROSPECTIVE ANALYSIS OF SUBAXIAL SUBLUXATION FOLLOWING ATLANTO-AXIAL ARTHRODESIS IN PATIENTS WITH RHEUMATOID ARTHRITIS

Ruifeng Yang^#, Shuhua Lan^#, Quanzhou Wu, Shuming Huang, Yuanhua Fang^*

Department of Orthopedics, Lishui Municipal Central Hospital (The Fifth Affiliated Hospital of Wenzhou Medical University), Lishui, Zhejiang 323000, China

Objective: To evaluate the association between A-A fusion angle and postoperative subaxial subluxation following atlantoaxial arthrodesis in patients with rheumatoid arthritis, and clarify the characteristics of SAS after surgery and to determine the optimal fusion angle for preservation of physiologic subaxial alignment.

Methods: 25 patients with cervical spine involvement in rheumatoid arthritis who underwent transarticular screw fixation between September 2015 and August 2017 in Lishui Municipal Central Hospital were retrospectively studied. Three patients died of complications unrelated to surgery 3 years after surgery. Ultimately, 20 of 22 patients had sufficient clinical data for the analysis. The patients included 15 females and 5 males. The duration of RA ranged from 5 to 30 years, with a mean duration of 12.5 years. The average patient age at surgery was 50.6 years (range 35-70 years). The research included 5 males and 15 females, whose average age was 50.4±5.6. Twenty patients with AAS treated with surgery were reviewed. In all patients, lateral cervical radiographs were obtained neutral, hyperflexion and hyperextension positions every year for 3 years after surgery. The cervical sagittal parameters were measured on X-ray, including C1-C2 angle, C2-C7 angle. We investigated the occurrence and progression of SAS using these annual radiographs.

Results: There were no significant differences between pre-and postoperative value in AAA and subaxial angle (SAA), respectively. Before surgery, SAS was found in 8 patients. The occurrence and progression of SAS after surgery was found in 9 cases (SAS P+ group). There were no significant differences in age, gender or the duration of RA between the SAS P+ group and the remaining 11 cases. We also found no differences in the pre-and post-op AAA and SAA between the two groups.

Conclusion: We did not find any relationships between the occurrence of SAS and the C1-C2 angle and C2-C7 angle before and after surgery. our findings suggest that select 20°±5° of C1-C2 angle in patients with atlantoaxial arthrodesis does not affect the occurrence of SAS at 3 years after surgery.