Factors of coxitis progression in patients with axial spondyloarthritis. Results of a two-year dynamic observation
Authors: Agafonova E. M. , Erdes Sh. , Dubinina T. V. , Demina A. B. , Smirnov A. V. 
Published: December 2024

Coxitis is one of the most common extra-axial manifestations of axial spondyloarthritis in Russia. According to studies conducted in the Russian Federation, the main factors leading to disability of patients with axial spondylitis (acSpA) is coxitis.

The aim of our study was to evaluate the factors of radiographic progression of coxitis in patients with axial spondylitis.

Material and methods. A prospective cohort study was conducted of 77 patients (23 women, 54 men) with axSpA (ASAS (Assessment of SpondyloArthritis International Society) criteria, 2009), observed for at least 2 years, with clinical and/or instrumental signs of coxitis. After 2 years, the patients again underwent a complete clinical, laboratory and instrumental examination (magnetic resonance imaging and pelvic survey). In all patients, the BASRI (Bath Ankylosing Spondylitis Radiology) Hip Index was determined for each hip joint (HJ). To assess the damage to the hip joint, the total stage of radiographic coxitis was used, to assess the rate of radiographic coxitis progression – a previously developed formula. To describe the data and their variability with a normal distribution of the feature, the arithmetic mean and standard deviation were used, and with an abnormal distribution of the feature or a small sample – the median, minimum and maximum values, interquartile range (Me [25th; 75th percentiles]). To assess the significance of differences between the analyzed groups, the Mann – Whitney U-test was used. To detect interrelated parameters, the Euclidean distance was determined using cluster analysis using the single linkage method. To detect the relationship between the clinical manifestations of axSpA and the radiographic progression of coxitis, a cluster analysis of the main parameters was performed.

Results and discussion. The median values of laboratory inflammation parameters – erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) – were high at baseline (20.0 mm/h and 14.5 mg/l, respectively). As for other clinical manifestations of the disease, 75% of 77 patients had peripheral arthritis at the time of inclusion in the study. The functional index of patients (BASFI, Bath Ankylosing Spondylitis Functional Index) was 3.3 at baseline. The average age of patients was 30.8±7.7 years with an average disease duration of 74.0±90.3 months. 72 (94%) patients were positive for HLA-B27. The BASRI Hip Index was assessed for each hip joint in all patients. The analysis showed that the most closely interrelated groups of clinical parameters are high clinical activity of the disease, the rate of radiographic progression of coxitis and the total stage of radiographic coxitis (Euclidean distance 100). It is also worth noting that the relationship between laboratory parameters of inflammation and disease activity indices is relatively weak, as well as with structural damage in axSpA.

Conclusion. Factors influencing the development and progression of coxitis in axSpA are a combination of such signs as high clinical activity of the disease, the presence of peripheral arthritis and male gender.