The epidemiology of osteoporosis and fractures in ankylosing spondylitis.

Bone is a target in many inflammatory rheumatic diseases. Inflammation leads to a wide range of changes in bone, and especially bone remodeling. In ankylosing spondylitis (AS) bone loss has been documented, but measuring bone density in the spine is hampered by new bone formation in syndesmophytes, periost and within the vertebrae. The risk of vertebral fractures is increased in AS. The diagnosis of vertebral fractures requires imaging and adequate evaluation of vertebral heights. In addition, in the ankysosed spine segments, additional imaging is often needed to diagnose spinal fractures at unusual locations (cervical spine) or in the posterior arch structures. Risk factors for vertebral fractures are helpful for case finding. Fracture prevention is indicated in high risk patients with AS, especially when they have already a vertebral fracture or in the presence of osteoporosis.