Mobility restriction in ankylosing spondylitis occurs mainly in early years of disease
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Interventions to prevent lumbar and thoracic movement restriction in patients with ankylosing spondylitis may require early intervention, as degradation seems to mainly occur in the first years of disease progression, a study found.
“The effect of age on spinal mobility is considerable, and using regression models, Ramiro et al. developed reference centile charts of the progressive age-related decline in spinal mobility among individuals without spinal impairment,” Kristina Hörnberg, RPT, PhD, of Umea University, in the Netherlands, and colleagues wrote in Arthritis Care and Research. “We have previously compared these norm data with that of a large AS study population to describe characteristics over a disease span of 40 years using repeated cross-sectional analyses, and also to define predictors of abnormal spinal mobility.
“Based on the assumption of a linear development of spinal mobility impairment at a group level in AS, we can further understand the content of our data through extended analyses of linear regression models,” they added.
To examine whether loss of spinal mobility occurred linearly in patients with AS, as well as compare AS-related mobility loss with that related to normal aging, Hörnberg and colleagues analyzed disease progression of 141 patients with AS, 30 of whom were women. Patients were followed for a median of 34 years and a total of 9,697 spinal mobility measurements were recorded. Patients recorded at least 10 visits with a treatment duration of at least 5 years, the researchers wrote.
The study included several spinal mobility tests and measurements — lateral spinal flexion (LSF), the 10 cm Schober test (ST10), chest expansion (CE) and cervical rotation (CR) were all assessed. After disease progressed passed a certain point, data were censored following a specific cutoff — 3 cm for LSF, 1 cm for ST10, 2 cm for CE and 10 degrees for CR — to prevent the bias of regression analysis, the authors wrote. Additionally, some data were not recorded for specific patients if they had no restriction of mobility in that measurement.
In all measured variables, the median values in patients with AS were significantly lower than the norm data, according to the researchers. The biggest difference between the normal expected range and that in patients with AS was measured in LSF and ST10. Overall, the reduction in spinal mobility over time stayed close to the anticipated value, except in the case of CR, which degraded at about twice the expected speed. There were no differences in the analysis between men and women.
In addition, the median deviations from individual regression lines were “significantly higher during the early phase of the disease,” with shrinking residuals over the follow-up period in LSF (P = .001) and CE (P > .001), the researchers wrote.
“After the first years of symptoms, a substantial impairment of mobility had occurred in LSF, the ST10, CE and CR,” Hörnberg and colleagues wrote. “Further declines in the LSF, the ST10 and CE were comparable to the age-related decrease seen in the general population. However, a continuous decrease exceeding the normal age-related decline, was seen in CR.
“Mobility restrictions related to AS seem to mainly occur during the first years of disease, which was before our data collection was initiated,” they added. “Our results indicate that measures taken to try to prevent lumbar and thoracic mobility restrictions would have to be introduced early in the course of the disease.”
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The study performed by Hörnberg and colleagues gives helpful insight into the progression of ankylosing spondylitis and solidifies the importance of early diagnosis and treatment in patients with AS. Since the window of opportunity to prevent decreased spinal mobility is early in the disease, emphasis should be placed on screening young patients with back pain for any signs of inflammatory spine disease.
Considering the possible progression of non-radiographic axial spondyloarthropathies to radiographic axial spondyloarthropathies, back pain among patients in their late teens to early 40s should not be dismissed, and an appropriate workup should be performed. Biologic treatment should be considered early to minimize or prevent decrease in spine mobility.
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Carlos M. Alonso, MD, FACR, RhMSUS
Ever since the introduction of biological DMARDs for the treatment of rheumatic diseases, our ability to alter the progression of disease has dramatically improved. In patients with rheumatoid arthritis, earlier treatment results in better long-term outcomes and less joint damage. Ankylosing spondylitis (AS) presents a special challenge due to the usually insidious onset of symptoms and delay in diagnosis.
This study showed that after the first 5 to 10 years of disease, the pace of deterioration in the lumbar and thoracic spine mobility was similar to the expected age-related decline.
However, the constant or starting point in measurements was lower in the AS group. This suggests that most of the thoracic and lumbar impairment occurs early in the disease process. Damage was most pronounced at the lumbar spine (measured by lateral spine flexion), followed by the thoracic spine (measured by the 10 cm Schober test). Cervical rotation was the only measure which continued to deteriorate faster than expected from the control group even after 10 years of disease.
This research paper illustrates that the window of opportunity for structural modification in AS occurs during the first few years of disease. Early detection of symptoms and use of disease modifying drugs is of the upmost importance in this population.
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David A. McLain, MD, MACR, FACP, FRCP
There is a familiar pattern in inflammatory rheumatic disease where there is a “window of opportunity” at the onset of inflammation and before permanent, irreversible damage occurs when intervention can make a significant difference in a patient’s life. The present study illustrates that loss of range of spinal motion has an accelerated decline in patients with ankylosing spondylitis. The researchers project that the decline is even faster in the early years of the disease. The “watch and wait” philosophy is to be avoided in these patients — as with rheumatoid arthritis, psoriatic arthritis, lupus, scleroderma, vasculitis, etc. — particularly now that we have effective medications for most of these diseases. One of the major challenges in rheumatology is improving access to care in a timely fashion. A challenge that is still not being addressed effectively.
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