Evaluation and Treatment of Ankylosing Spondylitis and Diffuse Idiopathic Skeletal Hyperostosis

Ankylosing spondylitis is a chronic inflammatory rheumatic disease of the axial skeleton and is the major subtype of diseases commonly referred to seronegative spondyloarthritides. Diffuse idiopathic skeletal hyperostosis is a noninflammatory skeletal disease characterized by ligamentous ossification of the anterolateral spine. Ankylosing spondylitis and diffuse idiopathic skeletal hyperostosis are distinct clinical entities, but both commonly cause back pain, stiffness, and decreased range of motion if disease progression results in spinal deformities. Both have extraskeletal manifestations that may be observed before diagnosis. The long-term course of these skeletal diseases results in structural changes that may lead to functional impairment and a decrease in quality of life. Advanced disease places patients at risk for fracture and neurological deficit. Spine surgeons will most likely see these patients late in the disease course once the structural changes have already occurred or as a result of trauma. It is important to identify these patients and initiate both treatment and lifestyle modifications to slow or halt disease progression and preserve patient functional status, thus avoiding debilitating sequelae. This chapter describes the current knowledge of disease prevalence, pathogenesis, genetics, clinical manifestations, diagnostic features, and nonsurgical management.