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Extended report
Development of new syndesmophytes and bridges in ankylosing spondylitis and their predictors: a longitudinal study
  1. Astrid van Tubergen1,
  2. Sofia Ramiro1,
  3. Désirée van der Heijde2,
  4. Maxime Dougados3,
  5. Herman Mielants4,
  6. Robert Landewé5,6
  1. 1Department of Medicine, Division of Rheumatology, Maastricht University Medical Center, Maastricht, The Netherlands
  2. 2Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
  3. 3Rheumatology B, Hôpital Cochin, Paris, France
  4. 4Department of Rheumatology, University Hospital Ghent, Ghent, Belgium
  5. 5Department of Medicine, Division of Rheumatology, Academic Medical Center Amsterdam, Amsterdam, The Netherlands
  6. 6Department of Rheumatology, Atrium Medical Center Heerlen, Heerlen, The Netherlands
  1. Correspondence to Dr Astrid van Tubergen, Rheumatologist, Department of Medicine, Division of Rheumatology, Maastricht University Medical Center, PO Box 5800, 6202 AZ Maastricht, The Netherlands; a.van.tubergen{at}


Background Structural damage of the spine in ankylosing spondylitis (AS) is associated with worse physical function and impaired spinal mobility. Knowledge about predictors of new syndesmophyte formation is limited.

Objectives To assess the development of new syndesmophytes at the level of individual vertebral bodies and to assess predictors for this development.

Methods Clinical and radiological data from 132 patients from the Outcome in Ankylosing Spondylitis International Study for whom complete sets of radiographs were available at baseline and at 2- and 4-year follow-up were used. Univariable and multivariable logistic regression analyses were performed to identify predictors associated with development of new syndesmophytes within 4 years.

Results At baseline, 81 (61%) patients had syndesmophytes. New syndesmophytes developed in 44 (33%) patients within 2 years and in 63 (48%) patients within 4 years. The RR of developing new syndesmophytes was 5.0 (95% CI 2.5 to 10.2) at 4 years in patients with existing syndesmophytes as compared with patients without. In the univariable analysis, older age, worse functional status, male gender, erythrocyte sedimentation rate and existing syndesmophytes were associated with development of new syndesmophytes at 4 years. In the multivariable logistic regression analysis, only the presence of existing syndesmophytes was a significant predictor (OR 18.72, 95% CI 6.44 to 54.42). When existing syndesmophytes were taken out from the model, age (OR 1.07, 95% CI 1.03 to 1.11) and male gender (OR 3.98, 95% CI 1.47 to 10.77) were statistically significant contributors.

Conclusion In AS, patients with existing syndesmophytes are prone to develop new syndesmophytes over time.

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  • Funding SR was supported by the Fundação para a Ciência e Tecnologia (FCT) grant SFRH/BD/68684/2010.

  • Competing interest None.

  • Ethics approval The study was approved by ethics committee from Maastricht University Medical Center.

  • Provenance and peer review Not commissioned; externally peer reviewed.