Wang T, et al. - Authors described the pelvic tilt change after spinal osteotomy in ankylosing spondylitis (AS) kyphotic deformity and assessed the impact on clinical outcomes. The patients included (2 women, 21 men) had a mean age of 39.8 ± 9.1 years. Spinal osteotomy corrected the abnormal pelvic tilt (PT) but it was hard to restore to theoretical normal value. In making surgery plan, PT is a helpful parameter. But, it is undesirable to pursue postoperative PT being totally equal to theoretical postoperative PT (tPT) and may even cause for overcorrection.