Later stages of ankylosing spondylitis are often associated with a hunchback, or kyphosis, which causes an imbalance in the sagittal plane of the spine. Patients may develop a hunchback deformity with intractable low back pain, which can seriously affect their quality of life because the kyphosis affects their ability to see and lie flat. Surgical treatment may be required at this time. Posterior pedicle subtraction osteotomy (PSO) is a common clinical procedure for the treatment of kyphosis in ankylosing spondylitis. PSO osteotomy in the lumbar segment was found to improve the spinal pelvic parameters more significantly while reducing the risk of spinal cord injury, and the related paper was published in the Chinese Medical Journal. （The PSO osteotomy is a V-shaped osteotomy through the pedicle, which is a closed osteotomy with no opening of the anterior edge, reducing the risk of tearing the large blood vessels anteriorly, and a large osteotomy contact surface, facilitating fusion. It is a closed osteotomy, which reduces the risk of tearing the large blood vessels anteriorly and has a large contact surface. It has become the most commonly used procedure to correct ankylosing spondylitis, mainly in patients with sagittal imbalance of the lumbar spine. The lumbar segment osteotomy, which is usually located at the end of the spinal cord, reduces the risk of spinal cord injury. At the same time, most patients with ankylosing spondylitis lose their lumbar anterior convexity, and osteotomy in the lumbar segment can significantly improve lumbar anterior convexity, improve the sagittal balance of the lumbar spine, and restore the normal sequence of the spine. The indications for surgery are mainly severe hunchback in ankylosing spondylitis with significant kyphosis, associated with intractable low back pain (poor drug effect), and some patients may have limited flat vision. However, if there is a significant hip flexion deformity in combination, treatment of the hip may be required before orthopedic surgery of the spine. The yellow angle in the figure below represents the position of the V-shaped osteotomy, and the L2 vertebral body becomes wedge-shaped after the osteotomy is closed. The white part is the pedicle screw and orthopedic rod.