What question did this study set out to answer?

April 11, 2026Open Access

A Reliable Prediction Method for the Pedicle Subtraction Osteotomy Angle in Ankylosing Spondylitis-Related Thoracolumbar Kyphosis: A Comparative Analysis with Existing Approaches

MQMu QiaoNanjing Drum Tower Hospital BQBang-ping Qian KWK Y WangUniversity of British Columbia

Key Points

The aim is to develop a new method for accurately predicting the pedicle subtraction osteotomy angle in ankylosing spondylitis patients while comparing its effectiveness with existing methods.
Analysis of 61 AS patients undergoing PSO
Use of AS-specific realignment criteria and Surgimap software
Comparison with three other predictive methods: FBI, trigonometric method, and ASKyphoplan
Evaluation of predictive methods using concordance correlation coefficient, accuracy rate, and RMSE
The new Surgimap method showed the highest prediction accuracy at 72.13%
Calculated bias was -2.36% with an RMSE of 8.34
Significant postoperative improvements in global kyphosis, lumbar lordosis, and SVA were observed
Undercorrection and overcorrection rates varied between low and high PI groups, reaching 80% accuracy in low PI patients

Abstract

Background: Careful preoperative planning regarding the reliable angle of pedicle subtraction osteotomy (PSO) in ankylosing spondylitis (AS) is beneficial for sagittal realignment, preventing undercorrection or overcorrection, and mitigating potential mechanical complications.The purpose of this study was to propose a novel method, using AS-specific realignment criteria and Surgimap software, for calculating a reliable PSO angle in AS patients with thoracolumbar kyphosis, and to compare its predictive accuracy with 3 other methods reported in the previous literature.Methods: Sixty-one AS patients who underwent 1-level PSO were analyzed, fulfilling the ideal sagittal balance criteria of adult spinal deformity at the final follow-up: pelvic tilt (PT) 108, T1 pelvic angle (TPA) 152.All the 4 methods were applied to calculate the theoretical angle of osteotomy (tAO) for each patient, including the trigonometric method, full balance integrated (FBI), SS-based ASKyphoplan, and Surgimap Spine plan.The difference between pre-and postoperative osteotomized vertebral angle in radiographs was defined as the actual angle of osteotomy (aAO).Precision of all predictive methods was evaluated on the basis of concordance correlation coefficient (CCC), accuracy rate, root mean squared prediction error (RMSE), and difference between tAO and aAO (bias).Results: Significant improvement in global kyphosis, LL, and SVA were noted postoperatively for all 61 patients without obvious correction loss at the final follow-up.The most accurate and precise method for the osteotomy angle calculation was the AS Surgimap plan (prediction accuracy, 72.13%; bias, -2.36%; RMSE, 8.34; CCC, 0.837), followed by FBI, the trigonometric method, and ASKyphoplan.The prediction accuracy, undercorrection rate, and overcorrection rate for the low and high PI groups were 80.00%, 5.71%, and 14.29% and 61.54%, 30.77%, and 7.69%, respectively.Conclusions: Surgimap Spine plan was relatively the most reliable and accurate approach to predict the PSO angle and achieve proper postoperative sagittal alignment for AS patients in comparison to other methods.Predetermined PT using the equation PT = (0.47 PI -7.5) and well-defined criteria (SSA > 108, SPA > 152, and TPA < 22) could improve the predictive values.

Ask AI

Helpful

Bookmark

View Full Paper