Vertebral Erosions Associated with Spinal Inflammation in Patients with Ankylosing Spondylitis Identified by Magnetic Resonance Imaging: Changes After 2 Years of Tumor Necrosis Factor Inhibitor Therapy

Objective. Spinal inflammation and erosions have been described in magnetic resonance imaging (MRI) examinations of patients with ankylosing spondylitis (AS). MRI scoring systems have implemented these observations. Methods. MRI scans (T1 or short-tau inversion recovery) from tumor necrosis factor-cc blocker (anti-TNF) trials with patients with active AS (n = 22) were analyzed at baseline and after 2 years based on vertebral units (VU). The analysis was based on the prevalence of spinal erosions in relation to inflammation (active erosions) or without it (inactive erosions) as an outcome measure on MRI and their course under anti-TNF therapy. The results of MRI scoring systems that include (ASspiMRI) or exclude (Berlin score) erosions were also compared. Results. At baseline, there were more VU with inflammation (33.7%) than with erosions irrespective of activity (10.6%). After 2 years, active erosions decreased to 3.7% while inflammation was seen in a total of 12% of VU - a reduction of 58.9% and 64.5%, respectively (both p < 0.02). The overall extent of erosions decreased from 10.6% at baseline to 5.6% at 2 years. At the patient level, 73% and 32% of patients showed active erosions (p = 0.002), while 100% and 64% of patients showed inflammation (p = 0.029) at baseline and 2 years, respectively. Both scoring systems showed similar improvement, independent of inclusion or exclusion of erosions. Conclusion Inflammation with erosions was observed in the spine of most patients with AS but their contribution to changes observed upon anti-TNF therapy was small, indicating that erosions do not need to be included in quantitative scoring systems of inflammation. Spinal inflammation was still present after 2 years of anti-TNF therapy in two-thirds of patients.