Introduction: Anterior lumbar interbody fusion (ALIF) is an effective procedure for correcting lordosis and restoring foraminal height. This study assesses whether intraoperative segmental lordosis (SL) achieved in the supine position change in postoperative upright alignment and examines how surgical technique and level treated impact the ability to achieve implant-specific lordosis and disc height targets.
Methods: Patients who underwent 1- or 2-level ALIF at a tertiary care center were included, excluding those with multi-level posterior fusion or pelvic fixation. Demographic and spinopelvic parameters were collected. Ideal SL and disc height were defined as the difference between listed cage parameters and actual postoperative changes, assessing alignment predictability and achievement of implant-specific goals.
Results: A total of 145 patients (mean age 57.4±12.1 years, 51.1% female) with 180 treated levels were analyzed. Of these, 90 (62.1%) had single-level treatment, and 55 (37.9%) had staged posterior fusion. SL increased significantly from preoperative to intraoperative (16.2±0.5° to 24.7±0.5°, p< 0.001) and was maintained postoperatively (24.2±0.6°, p=0.17). Compared to listed cage lordosis, the percentage achieved was lower at L4-5 than L5-S1 (39.5% vs. 62.0%, p=0.001), with staged posterior fusion improving lordosis achievement compared to ALIF alone (61.3% vs. 40.9%, p=0.006). Anterior disc height increased significantly from preoperative to postoperative (7.3±3.9 mm vs. 18.8±3.7 mm, p< 0.001), achieving 83.9% of listed cage height with staged fusion versus 72.8% with ALIF alone (p < 0.001).
Conclusion : In ALIF, the degree of correction achieved intraoperatively in the supine position is a reliable predictor of postoperative upright alignment. The L5-S1 level achieves a greater proportion of listed cage lordosis and height compared to L4-5, with staged posterior fusion further enhancing both lordosis and height outcomes. This study highlights the importance of surgical approach and treated level in achieving implant-specific alignment targets.
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