Calculation of the Correction Angle Required for Spinal osteotomy in Ankylosing Spondylitis Patients With Thoracolumbar Kyphosis: Validation of Three Predictive Methods

In AS patients with isolated thoracolumbar or lumbar kyphosis, both the SFA and FBI methods showed good agreement with the actual postoperative correction angle and can serve as reliable tools for preoperative planning. The HP method consistently overestimated the required correction, which may increase the risk of overcorrection; therefore, its application should be approached with caution and further refinement is warranted.