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). 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 < 0.001), postoperative-GT (28.9° vs 23.4°; P = 0.018), postoperative LApex location mismatched from ideal (77.8% vs 22.2%; P = 0.036), and postoperative R-type mismatched from ideal (67.6% vs 22.6%; P < 0.001) were significantly related to mechanical complications. The independent factors selected by multivariate analysis were: postoperative R-type mismatched from ideal OR 11.3 (95% CI   3.9-32.6; P < 0.001), age OR 1.05 (95% CI 1-1.1; P = 0.03), and LApex matching OR 0.5 (95% CI 0.27-0.97; P = 0.04). The further the LApex was from its ideal position, the higher the risk of mechanical complications (P = 0.036).

CONCLUSIONS

Over other multiple suspected risk factors, proper lumbar apex position and ideal sagittal shape restoration played an important role in postoperative mechanical complications after L-PSO.

LEVEL OF EVIDENCE

III.