Background A hallmark of ankylosing spondylitis (AS) is the progressive decline of spinal mobility. Recently published reference intervals (RI) for spinal mobility measurements in healthy individuals offer new possibilities to assess impairment during the course of the AS disease (1).
Objectives To evaluate the development of subnormal spinal mobility among patients with AS with regards to disease duration.
Methods The cohort comprised all patients born 1937 or later with a validated (modified NY criteria) AS diagnosis 1980–2015 at the Rheumatology department in Västerbotten, whom had one or more registered spinal mobility measurement (n=232). The first subnormal value (lower than the 2.5th percentile of healthy individuals) regarding 10 cm Schober test, lateral spinal flexion, chest expansion, and cervical rotation, respectively, using the age-, sex- and length specific reference intervals, was defined as outcome. The follow-up started at the first measurement and ended at the date of the outcome, the study end (June 30, 2015), death or the time point for the last visit + 2 years. The results were presented by Kaplan-Meier curves.
Results The median (range) of the total disease duration during follow-up was 31 (5–61) years. 3706 examinations were evaluated, with a median of 24 examinations/patient, or median (range) 1.0 (0.1–2.8) examinations/year of follow-up. The proportion of patients with subnormal mobility increased by disease duration for all measurements. Lumbar mobility was most impaired, but after 15–20 years half of the patients still had mobility measurements within the normal range (Figure 1).
Conclusions Preserved spinal mobility is common in long-standing AS. However, the results indicated a continuous progression of spinal stiffness also after 20 years of AS disease.
Ramiro S, van Tubergen A, Stolwijk C, et al. Ann Rheum Dis 2015;74:1218–1224.
Disclosure of Interest B. Sundström: None declared, L. Ljung Paid instructor for: Educational activities for BMS, Pfizer. Abbvie, S. Wållberg-Jonsson: None declared
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