Patients with ankylosing spondylitis commonly demonstrate impaired spinal mobility after 10 years of disease duration, at which time a weakened lateral spinal flexion becomes associated with a worse prognosis, according to recent findings in Arthritis Care & Research.
“Since the decrease of spinal mobility in AS is a slow process which progresses over decades, studies on spinal mobility over time are scarce and have been performed mainly in older materials,” Björn Sundström, RPT, PhD, of Umeå University in Sweden, and colleagues wrote. “Mobility decreases with age not only among individuals with AS but also among healthy individuals, where up to a 52% decrease in spinal mobility with increasing age has been described.”
“Despite that age and other factors affect the normal range of spinal mobility, the use of fixed reference values that are not adjusted is common when evaluating spinal mobility in AS in clinical practice,” they added. “Adjusted reference intervals for spinal mobility measurements have been derived from healthy individuals. These reference intervals enhance the quality of spinal mobility assessments during the course of the AS disease.”
To analyze spinal mobility impairment among patients with long-standing AS, Sundström and colleagues conducted a cross-sectional study of data accumulated at the Norrland’s University Hospital rheumatology department, in Västerbotten County, Sweden. There, spinal mobility measurements in patients with AS have been performed as part of routine care for nearly 4 decades. The researchers studied 3,849 measurements from 232 patients with AS, performed between February 1980 and June 2016.
These measurements — lateral spinal flexion, 10 cm Schober test, chest expansion and cervical rotation — were stratified by disease duration at 10-year intervals. They were then compared with published age and height adjusted spinal mobility reference intervals, along with fixed reference values typically seen in clinical practice.
According to the researchers, most patients exhibited at least one measurement, the most common being lateral spinal flexion, under the 2.5th percentile of the adjusted reference interval, after 10 years of living with AS. Additionally, in all measurements except cervical rotation, the researchers noted significant linear increases in the rate of patients with more than 40 years of disease duration who demonstrated impaired mobility. Lateral spinal flexion values that were less than the 2.5th percentile after ten years were linked to further spinal mobility issues.
“Impaired spinal mobility in AS is common after 10 years of disease and spinal mobility continues to deteriorate in the succeeding decades,” Sundström and colleagues wrote. “Early impairment of spinal mobility, although often limited in absolute numbers, is associated with a worse prognosis. The use of age- and height-adjusted reference intervals could significantly improve spinal mobility assessment during the course of AS disease. The use of fixed reference values lacks precision, overestimates the proportion with impaired spinal mobility in AS, must be used with extreme caution, or should preferably be avoided.” – by Jason Laday
Disclosures: Sundström reports no relevant financial disclosures. Please see the full study for additional author disclosures.