Prevalence and annual incidence of vertebral fractures in patients with ankylosing spondylitis

Abstract

To evaluate the prevalence and annual incidence of clinically-manifest vertebral fractures among patients with ankylosing spondylitis (AS). Coordinated by the Ankylosing Spondylitis International Federation, a self-administered general questionnaire which included some questions on gender, age, age at onset of disease, and a history of vertebral fracture was inserted in one issue of the membership journals of the AS patient organizations in Germany and Austria. Among the 1,071 patients responding who all had indicated that the diagnosis of AS had been established or confirmed by a physician, 61 (5.7%) indicated a history of vertebral fracture, 15 of them (1.4%) without an accident. The prevalence of vertebral fractures was 6.2% among male AS patients and 4.6% among females (NS), and 4.8% among HLA-B27+ patients and 9.9% among HLA-B27(-) patients (p<0.05). Spinal fractures occurred more often among AS patients with peripheral arthritis (7.1%) than among patients with axial involvement only (3.1%, p<0.01). The average delay between disease onset and diagnosis of AS was 10.5 years for patients with a vertebral fracture, compared to 8.7 years for patients without any such event (p<0.05). Among patients with a disease duration >or=42 years, the prevalence of vertebral fractures was 14%. The annual incidence of vertebral fractures which occurred without an accident had a maximum of 0.1% per annum at a disease duration of 20-35 years, whereas the incidence of vertebral fractures caused by an accident increased continuously with increasing disease duration, amounting to 1.3% per annum after a disease duration of 45 years. A considerable proportion of AS patients will experience a vertebral fracture during the course of the disease, in particular if peripheral joints are also involved.