Dynamic Changes of the Pelvis and Spine Are Key to Predicting Postoperative Sagittal Alignment After Pedicle Subtraction Osteotomy: A Critical Analysis of Preoperative Planning Techniques

Retrospective, radiographical analysis of mathe-matical formulas used to predict sagittal vertical axis (SVA) after pedicle subtraction osteotomy (PSO). Evaluate the ability of different formulas to predict SVA after PSO. Failure to achieve optimal spinal alignment after spinal fusion correlates with poor outcomes. Numerous mathematical models have been proposed to aid preoperative PSO planning and predict postoperative SVA. Pelvic parameters have been shown to impact spinal alignment; however, many preoperative planning models fail to evaluate these. Compensatory changes within unfused spinal segments have also been shown to impact SVA. Predictive formulas that do not evaluate pelvic parameters and unfused spinal segments may erroneously guide PSO surgery. A formula that integrates pelvic tilt (PT) and spinal compensatory changes to predict optimal SVA has been previously proposed. Comparative analysis of 5 mathematical models used to predict optimal postoperative SVA (