Instrumental diagnosis of coxitis in ankylosing spondylitis in real clinical practice

Abstract

Coxitis is one of the most common extra-axial manifestations of ankylosing spondylitis (AS). Most Russian studies consider hip joint (HJ) involvement in AS patients as a major factor of poor prognosis in this disease. All detected hip joint changes are characterized by one term «coxitis». Until recently, there has been no clarity on inflammation of which structures of HJ leads to its destruction. This problem can be solved by prospective studies. A start was made by the V.A. Nasonova Research Institute of Rheumatology on the study of the evolution of coxitis in AS in 2013. This communication is devoted to the results initially identified by various imaging techniques for detecting HJ changes.Objective:to study the characteristics of HJ injury in AS, which have been detected by different imaging techniques.Subjects and methods.The investigation enrolled 125 AS patients, including 84 men (a male/female ratio of 2:1). The mean age of the patients was 31.4±9.1 years; the mean age at disease onset – 24.6±4.4 years; the median duration of AS at the time of examination – 96 (12–444) months. The HLA-B27 antigen was present in the majority of patients (94%). AS activity defined by ASDAS-CRP and BASDAI was high; BASFI scores averaged 3.4±2.1. All the patients underwent the following instrumental examinations: plain pelvis radiography, HJ ultrasound and magnetic resonance imaging (MRI).Results and discussion.The clinical, ultrasound, and MRI signs of coxitis were found in 82, 75, and 88% of cases, respectively; coxitis was radiologically confirmed only in 50% of patients. This disease was diagnosed by several techniques in the vast majority of cases. The diagnosis of coxitis was based only on clinical signs in only three (2%) patients. In approximately every sixth (16%) patients with AS, who had clinical signs of coxitis, the latter was verified only by one of the instrumental techniques (ultrasonography, radiography, or MRI). Our findings demonstrated that more than half of patients had high coxitis activity, and more prolonged coxitis was responsible for higher X-ray HJ changes and functional limitations.Conclusion.Our study has showed that the instrumental techniques used to diagnose coxitis are not equivalent in evaluating HJ injury. To decide which of them is more effective in screening and predicting the course of coxitis, there is a need for further prospective investigations.