Fig. 1

A 31-year old male with AS. a The preoperative X-ray showed that the parietal vertebrae were located at L1, which belonged to the lumbar lordosis group. b) Single-segment pedicle subtraction osteotomy (PSO) was conducted at T12. Lumbar lordosis, global kyphosis, and sagittal vertical axis improved from the preoperative –44°, 86°, and 162.29 mm to –45°, 47°, and 24.41 mm, respectively. c) At the last follow-up in the 16th-month post-operation, no apparent orthopedic loss was observed, and lumbar lordosis, global kyphosis, and sagittal vertical axis were –41°, 53°, and 30.67 mm, respectively