Risk Factors for the Development and Progression of Atlantoaxial Subluxation in Surgically Treated Rheumatoid Arthritis Patients, Considering the Time Interval between Rheumatoid Arthritis Diagnosis and Surgery

Abstract

Objective: Rheumatoid arthritis (RA) is a systemic disease that can affect the cervical spine, especially the atlantoaxial region. The present study evaluated the risk factors for atlantoaxial subluxation (AAS) development and progression in patients who have undergone surgical treatment.

Methods: We retrospectively analyzed the data of 62 patients with RA and surgically treated AAS between 2002 and 2015. Additionally, we identified 62 patients as controls using propensity score matching of sex and age among 12667 RA patients from a rheumatology registry between 2007 and 2015. We extracted patient data, including sex, age at diagnosis, age at surgery, disease duration, radiographic hand joint changes, and history of methotrexate use, and laboratory data, including presence of rheumatoid factor and the C-reactive protein (CRP) level.

Results: The mean patient age at diagnosis was 38.0 years. The mean time interval between RA diagnosis and AAS surgery was 13.6±7.0 years. The risk factors for surgically treated AAS development were the serum CRP level (p=0.005) and radiographic hand joint erosion (p=0.009). The risk factors for AAS progression were a short time interval between RA diagnosis and radiographic hand joint erosion (p<0.001) and young age at RA diagnosis (p=0.04).

Conclusion: The CRP level at RA diagnosis and a short time interval between RA diagnosis and radiographic hand joint erosion might be risk factors for surgically treated AAS development in RA patients. Additionally, a short time interval between RA diagnosis and radiographic hand joint erosion and young age at RA diagnosis might be risk factors for AAS progression.

Keywords: Atlantoaxial subluxation; Posterior cervical fusion; Rheumatoid arthritis.

Fig. 1. The number of surgically treated patients stratified into 6 categories based on a 5-year time interval between RA diagnosis and AAS surgery. A total of 53 (85.4%) patients underwent surgical treatment less than 20 years after RA diagnosis. RA : rheumatoid arthritis, AAS : atlantoaxial subluxation.

Fig. 2. A : In scatterplot graph, the linear regression line shows a statistically significant overall gradual upward slope, which means the time to surgery reduces by 1.658 years when the time to radiographic hand joint erosion reduces by 1 year. B : In scatterplot graph, the linear regression line shows a statistically significant overall gradual upward slope, indicating that patients who started MTX early required early surgery. C : The boxplot graph shows the mean time interval between RA diagnosis and AAS surgery was 4.7 years greater in female patients than in male patients. D : In scatterplot graph, the linear regression line shows an upward trend, indicating that patients who are diagnosed with RA at a young age might require early AAS surgery. RA : rheumatoid arthritis, AAS : atlantoaxial subluxation.