Ideal sagittal profile restoration and ideal lumbar apex positioning play an important role in postoperative mechanical complications after a lumbar PSO

Study design Retrospective analysis of prospectively collected data. Objective To determine the influence of postoperative ideal lordosis distribution and ideal sagittal harmony on mechanical complications in patients undergoing one-level lumbar pedicle subtraction osteotomy (L-PSO). Summary of background data Many variables have been associated with mechanical complications after L-PSO. However, the impact of restoring the ideal inflexion point, lumbar apex, and sagittal shape is still underexplored. Methods Analyzed risk factors were: age and patient-related variables, PSO level, interbody cages, rod material/diameter, number of rods, upper instrumented vertebra, lower instrumented vertebra, PI-LL mismatch, global tilt (GT), postoperative level of lumbar apex (LApex), postoperative level of inflexion point (InfxP), and postoperative type of Roussouly sagittal profile (R-type). These last variables were compared to ideal (based on pelvic incidence). Univariate and multivariate analyses were performed to identify risks for mechanical complications with a minimum 2-year follow-up. Results A total of 87 patients were included. Mean follow-up was 4.5 ± 1.7 years. 40.2% of the patients suffered postoperative mechanical complications (7 PJK, 4 PJF, 18 pseudoarthrosis/rod breakage, 6 screw pullout). Mean time for complications was 584 ± 416 days from surgery. Univariate analysis showed that age (63 vs 57 years; P = 0.04), BMI (28.1 vs 25.9; P = 0.024), preoperative-GT (50.7° vs 38.7°; P