Predicting Syndesmophyte Formation in Axial Spondyloarthropathy
Tochukwu Anachebe (1), Gillian Fitzgerald (1,2), Ronan Mullan (3), David Kane (3), Finbar O’ Shea (1).
(1) Department of Rheumatology, St. James’s Hospital. (2) Department of Medicine, Trinity College Dublin (3) Department of Rheumatology, Tallaght University Hospital
Axial spondyloarthropathy (axSpA) is an inflammatory arthritis, which can result in syndesmophytes (new bone formation) and complete ankylosis of the spine. The pathogenesis of syndesmophytes is incompletely understood. Presence of baseline syndesmophytes predict further syndesmophytes, but other predictive factors have been difficult to define. The impact of extra-articular manifestations (EAMs) on syndesmophyte formation is unclear.
1. Assess the burden of radiographic disease in axSpA
2. Determine variables associated with syndesmophytes, specifically investigating the effect of EAMs.
A cross-sectional study of AxSpA patients was performed, comprising standardised clinical assessment and structured interviews. Lateral x-rays of the lumbar and cervical spine were performed to quantify syndesmophytes using a validated score (mSASSS) ranging from 0-72, with higher numbers indicating a higher burden. BASRI-hip was used to determine hip involvement, assessed on x-ray of pelvis.
One hundred and four patients with axSpA were included: 78.8% (n=82) male, 98.1% (n=102) Caucasian, average (SD) age 50.8 (12) years, average disease duration 25 (13) years, EAM prevalence 29.1% (n=30). Uveitis was the most prevalent EAM (29%), followed by inflammatory bowel disease (IBD) (18.4%) and psoriasis (17.5%).
Median (IQR) mSASSS was 9.5 (33.8), 10.6% (n=11) of patients had an mSASSS of 0 and 7.7% (n=8) had a bamboo spine. Increasing mSASSS correlated significantly (p<0.05) with increasing age (rho=0.6), longer disease duration (rho=0.5), rising BASMI (rho=0.8), higher BASFI (rho=0.4) and higher HAQ (rho=0.3). Patients with moderate or severe hip disease, as measured by BASRI, were more likely to have a higher mSASSS score (OR 3.8, 95% CI 1.5-9.3).
Patients with hypertension had higher median mSASSS score than patients without (25.4 v 7, p<0.01). Gender, HLA-B27 status, smoking, hypercholesterolaemia, ischaemic heart disease and diabetes had no impact on mSASSS.
The presence or absence of uveitis, psoriasis or IBD had no effect on syndesmophyte formation. Equally, peripheral arthritis had no effect.
In keeping with previous literature, higher mSASSS was associated with more severe disease. However, in contrast to other published studies, gender had no effect on the severity of mSASSS in our cohort. EAMs did not affect the mSASSS score, but worse hip disease did. It remains a challenge to predict which patients will develop syndesmophytes.