Introduction: Anterior lumbar interbody fusion (ALIF) is a common procedure for optimizing sagittal parameters in lumber spine. This study aims to identify factors that predict postoperative segmental lordosis (SL), focusing on spinopelvic parameters and implanted cage parameters.
Methods: Patients who underwent 1- or 2-level ALIF at a tertiary care center were identified. Details were extracted on demographics and spinopelvic parameters. Postoperative SL was assessed and compared with preoperative SL using the Wilcoxon signed-rank test. Multivariable linear regression was performed to identify independent predictors of postoperative SL.
Results: 150 patients (mean age 57±12.5 years, 53.6% female) with 207 treated levels were analyzed. Of these, 93 (62%) had a single level treated, and 100 (66.7%) underwent staged posterior fusion. SL significantly increased from pre- to postoperative radiographs (16.3±7.5° vs 24.2±7.9°, p< 0.001), achieving an average 52.5% of the listed cage lordosis. In multivariable analysis, postoperative SL was predicted by patient age (β=0.09°/yr, 95% CI [0.01, 0.16], p=0.03), preoperative SL (β=0.52° per degree, 95% CI [0.33, 0.72], p< 0.001), implant lordosis (β=0.36° per degree, 95% CI [0.1, 0.64], p=0.01), two-level implantation (β=-4.44°, 95% CI [-6.87, -2.01], p< 0.001), L5-S1 implantation (β=3.83°, 95% CI [1.35, 6.32], p< 0.001), and staged posterior fusion (β=2.43°, 95% CI [0.67, 4.20], p=0.01). These variables remained predictive with positive correlation when analyzing the difference between pre- and postoperative SL. However, greater preoperative SL predicted lower ΔSL (β=-0.45° per degree, 95% CI [-0.65, -0.26], p< 0.001). Other spinopelvic or cage parameters did not significantly predict postoperative SL or changes in SL.
Conclusion : Preoperative segmental lordosis, listed cage lordosis, the number of treated levels, the anatomic level implanted, and the use of an adjunct posterior approach are key predictors of postoperative SL. Additionally, patients with higher preoperative lordosis are more likely to experience a smaller postoperative change in SL.
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