title: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: University of Amsterdam, Amsterdam, The Netherlands, and Hospital Garcia de Orta, Almada, Portugal.
authors.forename: Sofia
authors.initials: S
authors.lastname: Ramiro
authors.affiliation: Amsterdam Rheumatology Center, University of Amsterdam, Amsterdam, and Atrium Medical Center, Heerlen, The Netherlands.
authors.forename: Robert B M
authors.initials: RB
authors.lastname: Landewé
authors.affiliation: Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Désirée
authors.initials: D
authors.lastname: van der Heijde
authors.affiliation: Maastricht University Medical Center and University of Maastricht, Maastricht, The Netherlands.
authors.forename: Carmen
authors.initials: C
authors.lastname: Stolwijk
authors.affiliation: Paris Descartes University, Cochin Hospital, AP-HP, INSERM (U1153), PRES, Sorbonne Paris-Cité, France.
authors.forename: Maxime
authors.initials: M
authors.lastname: Dougados
authors.affiliation: Ghent University Hospital and Ghent University, Ghent, Belgium.
authors.forename: Filip
authors.initials: F
authors.lastname: van den Bosch
authors.affiliation: Maastricht University Medical Center and University of Maastricht, Maastricht, The Netherlands.
authors.forename: Astrid
authors.initials: A
authors.lastname: van Tubergen
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D038622:Internationality; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D016059:Range of Motion, Articular / Q000502:physiology*; D013131:Spine / Q000502:physiology*; D013167:Spondylitis, Ankylosing / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D013223:Statistics as Topic / Q000639:trends*; D013997:Time Factors