Spinal fractures related to ankylosing spondylitis : Epidemiology, clinical outcome and biomechanics

Background: Spinal fractures related to ankylosing spondylitis (AS) are often associated with serious complications. Therefore, knowledge of the incidence, best treatment, outcome, and prevention would assist in improving current guidelines. Objectives: This thesis aims at (1) analysing the complications and mortality of surgical treatment, (2) mapping the incidence and treatment modalities for these patients in Sweden, as well as (3) investigating the putative preventive effect of biological disease modifying anti-rheumatic drug (bDMARD) therapy on spinal fractures related to AS. Methods: Merged multiple national registries were used to identify predictors of mortality and spinal fractures in patients with AS. Beyond that a finite element model (FEM) was designed to simulating a cervicothoracic fracture related to AS. Results and Conclusions: During the last two decades an increase of the incidence of vertebral fractures in patients with AS was observed. With the introduction of bDMARD treatment of AS was revolutionised and quality of life and function improved. It seems that the improved quality of life and function in these patients does not correlate with a reduced fracture risk. Still, for the first time a beneficial effect of bDMARD with regard to spinal fracture occurrence was provided. The risk of spinal fractures was not reduced, but the debut of a spinal fracture was delayed with bDMARD. Since for this study the observation interval was only a decade, a future follow-up should revisit the effect of bDMARD on spinal fractures related to AS. Furthermore, it was shown that posterior stabilisation is an effective method for restoring stability without the necessity of additional external fixation. Most likely the early rehabilitation reduced pulmonary complications, which in turn reduced early mortality of these fractures. The FEM could be used to identify the most appropriate implant configuration, since no well-established cadaver models exist. Clinical Trial Registration: ClinicalTrials.gov, Identifier NCT02840695