Sacroiliac Joint Ankylosis In Young Spondyloarthritis Patients Receiving Biologic Therapy: Observation of Serial MRI scans

Objectives: To assess the temporal relationship between initiating biologic therapy and magnetic resonance imaging (MRI) scores of inflammation and structural damage in young patients with spondyloarthritis. / Methods: A local adolescent rheumatology database was searched for patients aged 12 – 24 years with sacroiliitis on MRI and a clinical diagnosis of enthesitis‐related arthritis (ERA) or non‐radiographic axial spondyloarthritis. Patients treated with tumour necrosis factor inhibitor (TNFi) therapy with a minimum of one scan before and two after starting TNFi therapy (over ≥ 2 years) were included. Images of the sacroiliac joints were scored for inflammation and structural abnormalities (including erosions, fat metaplasia and fusion). The effects of TNFi therapy and of time since initiation of TNFi therapy on inflammation and structural abnormalities were assessed using a mixed‐effects regression analysis. / Results: Twenty‐nine patients aged 12‐23 years undergoing TNFi therapy were included. Inflammation scores were significantly lower in patients on treatment (P=0.013), but there was no significant effect of time from TNFi initiation on inflammation (P=0.125). Conversely, there was no significant effect of treatment itself on fusion scores (P=0.285), but fusion scores significantly increased with time from TNFi initiation (P=0.000). A similar pattern was observed for fat metaplasia. Fusion scores did not change in the first year after starting TNFi therapy (P=0.108), but were significantly increased at all subsequent time points (P=0.000 to 0.001). / Conclusions: TNFi therapy failed to prevent the eventual development of joint ankylosis in this cohort, despite a substantial reduction in inflammation with TNFi therapy.