Patients with ankylosing spondylitis suffering from AO Type B3 traumatic thoracolumbar fractures are associated with increased frailty and morbidity when compared with patients with diffuse idiopathic skeletal hyperostosis

Terence Tan, Milly S. Huang, Martin K. Hunn, Jin Tee


Background: AO Type B3 hyperextension thoracolumbar fractures are the commonest fracture subtype in ankylosing spinal disorders. Although often considered together in spinal fractures, ankylosing spondylitis (AS) and diffuse idiopathic skeletal hyperostosis (DISH) are distinct spondyloarthropathies with different pathophysiology. Few studies have compared the two entities in the setting of traumatic thoracolumbar fractures. The authors compare demographic metrics, injury profile, clinical and radiographical outcomes between patients with AS and DISH in patients suffering from AO Type B3 traumatic thoracolumbar fractures.
Methods: From January 2008 to December 2018, a retrospective analysis of consecutive surgically-managed patients with AO Type B3 fractures was performed. Demographic metrics, co-morbidity [Charlson-comorbidity index, modified frailty index (mFI), etc.], injury profile (level of injury, mechanism of injury, etc.), clinical (postoperative complication, etc.) and radiographical variables were collected. Differences between patients with AS and DISH were compared.
Results: Fourteen patients were identified. All patients had AS (n=6) or DISH (n=8). The mean age was 72.8±10.2 years and 78.6% of patients were neurologically intact at presentation. Medical and/or surgical complications occurred in 10 of 14 (71.4%) patients. As compared to patients with DISH, patients with AS were more likely to have low falls as the injury mechanism [odds ratio (OR): 35.0, P=0.026], have higher mFI (OR: 30.6, P=0.015), and experience a higher number of postoperative complications per patient (AS: 1.8/patient vs. DISH: 0.5/patient, P=0.024).
Conclusions: In the setting of AO Type B3 fractures, patients with AS are more frail and have higher in-hospital morbidity compared to patients with DISH. Despite both pathologies being ankylosing in nature, further studies are required to fully understand the clinical differences between the two entities to enable clinicians to apply a more targeted and nuanced approach in managing fractures in ankylosing spinal disorders.