Predictive Accuracy of Surgimap Surgical Planning for Sagittal Imbalance: A Cohort Study

Study Design. A cohort study.Objective. To evaluate the predictive value of surgical planning using Surgimap regarding postoperative sagittal alignment.Summary of Background Data. Surgical planning in sagittal imbalance is recognized as a key step of treatment to ensure results.Methods. The study involved 40 nonconsecutive patients who underwent surgery for sagittal misalignment. Postoperative alignment measured by sagittal vertical axis (SVA) and pelvic tilt was considered the gold standard. Surgimap prediction of final alignment was considered the test. Planning and postoperative films were classified as properly and improperly aligned. Sensitivity, specificity, and positive and negative predictive values of Surgimap planning [using two different methods: direct simulation (method A) and simulation after correction of pelvic tilt to 20 degrees (method B)] to detect postoperative improper alignment were calculated.Results. Seventeen (42.5%) of 40 patients had proper postoperative alignment. According to method A, a proper alignment was achieved in 13 patients [S = 76.5%, Sp = 73.9%, RR = 2.93 (95% confidence interval, CI 1.40; 6.12), P < 0.001]; According to method B, a proper alignment was achieved in 15 patients [S = 88.2%, Sp = 60.9%, RR = 2.25 (95% CI 1.32; 23.86), P < 0.001]. Kappa statistics indicate moderate agreement between actual postoperative alignment and computer prediction.Conclusion. The ability of Surgimap to predict proper postoperative sagittal alignment was excellent in this cohort. Its ability to predict proper alignment was improved by correction of pelvic tilt to 208 during planning.