Time course of radiographic hip joint changes in patients with early axial spondyloarthritis

Abstract

The diagnosis of coxitis remains one of the most difficult problems in the management of patients with axial spondyloarthritis (axSpA). In Russia, almost every two patients with axSpA were found to have hip joint (HJ) damage. However, until a certain time, there have been no methods to estimate the rate of progression of radiographic HJ changes in clinical practice. We have previously developed a formula for calculating the rate of coxitis progression, which simplifies the assessment of radiographic HJ changes and allows a physician to make a timely decision about changing therapy if rapidly progressing coxitis is detected.Objective: to estimate the rate of radiological progression of coxitis during a 24-month follow-up of patients with early axSpA.Patients and methods. Examinations were made in 38 patients (20 women and 18 men) who had been followed up for at least 2 years without radiographic and ultrasound signs of HJ joint involvement. The patients' mean age was 28.8±5.5 years; the disease duration was 22.7±15.7 months. HLA-B27 was positive in 35 (92%) patients. The summary stage of radiographic coxitis (ssRC) was used to assess HJ damage; the previously developed formula was applied to estimate the rate of radiological progression of coxitis (R-rpC).Results and discussion. The median cervical-capsular distance (CCD) was 5.2 mm at baseline and 4.9 mm at 2 years (p7 mm increase in the CCD. The mean ssRC was 0.34±0.75 scores at base line, 0.86±0.78 scores at 1 year; and this indicator increased up to 1.24±1.36 scores at 2 years (p=0.004). During 2 years of follow-up, there was no coxitis progression (the difference between ssRC2 and ssRC1 was 0) in 24 (63%) patients; ΔssRC increased by 1 score in 5 (13%); by 2 scores in 6 (16%), and by 4 scores in 3 (8%). On patient inclusion to the investigation, R-rpC averaged 0.5 (it was conventionally assumed that patients had no signs of HJ damage at the disease onset (ssRC=0). During therapy for the underlying disease, the mean R-rpC was 0.3 and 0.2 score/year within the first and second years, respectively. The mean R-rpC in the ΔssRC >0 group was as many as 0.85 score/year at one-year follow-up and 0.53 score/year at two-year follow-up.Conclusion. The developed procedure for estimating the progression of coxitis using ssRC is easy to use and can identify patients at high risk for coxitis progression.