• Haku Iizuka, Yoichi Iizuka, Tokue Mieda, Ryoichi Kobayashi, Masahiro Nishinome, Tsuyoshi Ara, Yasunori Sorimachi, Takashi Nakajima, and Kenji Takagishi.
• Department of Orthopedic Surgery, Gunma University Graduate School of Medicine, 3-39-22, Showa, Maebashi, Gunma 371-8511 JAPAN.
• Clin Spine Surg. 2016 Jun 28.

Study DesignRetrospective study.ObjectiveThe purpose of this study was to investigate the incidence of subaxial subluxation (SAS) following atlanto-axial arthrodesis in RA patients using annual radiographs obtained for five years and clarify the characteristics of SAS after surgery.Summary Of Background DataRheumatoid SAS has been reported to occur following atlanto-axial arthrodesis. Many authors have noted that excessive correction of the atlanto-axial angle (AAA) results in a decrease in subaxial lordosis, thereby inducing SAS; therefore, we paid special attention to acquiring a suitable AAA in patients with atlanto-axial arthrodesis.MethodsTwenty-five patients with AAS treated with surgery were reviewed. In all patients, lateral cervical radiographs were obtained neutral, maximal flexion and maximal extension positions every year for five years after surgery. We investigated the occurrence and progression of SAS using these annual radiographs.ResultsThere were no significant differences between pre- and postoperative value in AAA and subaxial angle (SAA), respectively. Before surgery, SAS was found in 10 patients. The occurrence and progression of SAS after surgery was found in 12 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 13 cases. We also found no differences in the pre-and post-op AAA and SAA between the two groups.ConclusionAlthough SAA was maintained following atlanto-axial arthrodesis in RA-AAS patients, 12 of 25 patients (48%) with AAS developed SAS following atlanto-axial fusion. Further surgery was not needed for SAS up to five years after the initial surgery. We did not find any relationships between the occurrence of SAS and the AAA and SAA before and after surgery. Therefore, our findings suggest that proper reduction of AAA in patients with atlanto-axial arthrodesis does not affect the occurrence of SAS at five years after surgery.

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