Qiao M, et al. - This study is performed to assess the durability of surgical outcomes and the patterns of loss of correction in thoracolumbar kyphosis secondary to ankylosing spondylitis (AS) following lumbar pedicle subtraction osteotomy (PSO) with over 5-year follow-up. For treating AS-related thoracolumbar kyphosis, PSO was an effective procedure and had a potential for maintaining sustained surgical outcomes during the middle-term follow-up. In this study, the loss of correction was mainly attributable to non-instrumented segments without fully ossified bridging syndesmophyte in the thoracolumbar region instead of instrumented levels.