Hierarchy of Impairment of Spinal Mobility Measures in Ankylosing Spondylitis: Twelve‐Year Data

Abstract

Objective. To investigate which spinal mobility measures (SMMs) are most frequently impaired in patients with ankylosing spondylitis (AS), whether a hierarchy of impairment can be established, and whether assessing fewer measures sufficiently captures impairment in spinal mobility. Methods. Patients from the Outcome in Ankylosing Spondylitis International Study were followed up for 12 years. SMMs were considered impaired when falling below predefined cutoffs, derived from normal individuals. The proportion of patients in whom each SMM was impaired was calculated using baseline observation. In patients with ‡1 impaired SMM, we investigated how often impairment in spinal mobility would be missed if only a fixed number of SMMs was assessed. Analyses were repeated using all 12-year observations. Results. A total of 216 patients were included (70% males). Lateral spinal flexion (LSF) was the most frequently impaired measure, followed by the modified Schober (mSchober) test, tragus-to-wall, cervical rotation, intermalleolar distance, and chest expansion measures, respectively. This hierarchy was strikingly consistent over time, and independent of sex, symptom duration, and presence of syndesmophytes. In patients with ‡1 impaired SMM, LSF was impaired most frequently (86%), followed by the mSchober test (58%). If only LSF was measured, 14% of patients with impairment in any SMM would be missed; if additionally the mSchober test was measured, 9% would be missed. Conclusion. LSF followed by the mSchober test are the most frequently impaired mobility measures in AS, reflecting an earlier involvement of the lumbar spine, followed by involvement of the thoracic and cervical spine. In clinical practice LSF and the mSchober test suffice to screen impairment in spinal mobility.

Frequency of Impaired Spinal Mobility in Patients with Chronic Back Pain Compared to Patients with Early Axial Spondyloarthritis

“…In the current study, the most frequently impaired mobility measure in the axSpA group was lateral spinal flexion (35%), followed by chest expansion (20%), while the other mobility measures had lower proportions of impairment (12-15%). Lateral spinal flexion has also been reported to be the most frequently impaired mobility measure in established AS (27), but unlike in our early cohort the second most frequently impaired measures were found to be lumbar flexion and tragus-to-wall/occiput-to-wall distance (27). This finding may indicate that there is a different pattern of mobility impairment in early disease compared to late disease.…”

“…This finding may indicate that there is a different pattern of mobility impairment in early disease compared to late disease. It has been suggested that screening for impairment in mobility in AS can be done by assessing lateral spinal flexion and lumbar flexion (27). However, our results do not support screening with only these measures, since 28% ( Even though the proportion of patients with impaired spinal mobility was similar in the subgroups, patients with axSpA showed to had better cervical rotation and intermalleolar distance than patients with other causes of chronic back pain.…”

“…Even so, in our current study 2 out of 3 of patients with chronic back pain had impaired mobility in 1 or more measures, defined as below the fifth percentile of the general population. In a previous study, a similar comparison was made for patients with established AS (27), with an even stricter cutoff between normal and impaired mobility (2.5 th percentile). This study showed that 79% of the patients with AS had impaired spinal mobility compared to the general population (27), reflecting that restricted spinal mobility is more prevalent in patients with established AS.…”

Is radiographic progression in radiographic axial spondyloarthritis related to matrix metalloproteinase degradation of extracellular matrix?

“…Details of the radiograph readings, imputation of missing vertebral corners and reliability have been reported elsewhere. 17 The radiographs from the visit of biomarker assessment (here designated as ‘baseline’, see below) and 2 years later were used. Radiographic progression was calculated as the difference in the mSASSS between the two radiographs (baseline subtracted from year 2).…”

Incorporating assessment of the cervical facet joints in the modified Stoke ankylosing spondylitis spine score is of additional value in the evaluation of spinal radiographic outcome in ankylosing spondylitis

“…Longitudinal studies on the course of spinal mobility showed that the majority of patients with AS develop moderate to severe impairment of spinal mobility. Patients with severe spinal restrictions had severe spinal deformity [13, 14]. Due to the anatomy of the facet joints, damage to these joints results in reduced cervical rotation [12].…”