Modified Ondra's Formula to Predict Post-Op SVA after Lumbar PSO: A Preliminary Report Verified by Simulated Post-op Images Via Surgimap Software.

Aim: This study aimed to introduce a new mathematical formula to predict sagittal vertical axis (SVA) changes after lumbar pedicle subtraction osteotomy (PSO).

Material And Methods: This cross-sectional study included 43 patients. Lateral full spinal radiographs were exported from Picture Archiving and Communicating Systemand imported to Surgimap (NemarisInc,New York, NY, version 2.