Park JS, et al. - Here, the authors described cases of sagittal translation that developed after pedicle subtraction osteotomy (PSO) in patients with ankylosing spondylitis (AS) with kyphotic deformity and examined risk factors for sagittal translation. In patients with AS, the incidence of sagittal translation after PSO was closely associated with severity of ankylosis. Surgeons, therefore, ought to take into consideration the sagittal translation, which could induce neurologic complications, when PSO was performed for AS patient with severe ankylosis.