Comprehensive analysis of biomechanical stability and clinical efficacy in oblique lumbar interbody fusion with distinct anterolateral fixation modalities.

OBJECTIVE The aim of this study was to evaluate the clinical and biomechanical effects of distinct anterolateral screw placement angles in oblique lumbar interbody fusion combined with anterolateral fixation (OLIF-AF), focusing on cage subsidence (CS) incidence, spinal stability, and optimal fixation strategies.

METHODS Patients who underwent OLIF-AF at a single center from December 2017 to November 2023 were retrospectively analyzed. Patients were divided into 4 groups (G0, G1, G2, and G3) based on the coronal plane angle (CPA) and relative horizontal plane angle. Preoperative and 1- or 3-day, 3-month, and 12-month postoperative radiological and clinical data were collected. A validated L4-5 finite element model simulated 4 screw configurations under 6 loading conditions.

RESULTS Eighty patients (49 female, mean age 64.5 ± 7.1 years) were included in the analysis (28, 23, 15, and 14 patients in groups G0, G1, G2, and G3, respectively). CS occurred in 48.75% of patients, with significantly higher rates in the G2 (86.67%) and G3 (71.43%) versus G0 (28.57%) and G1 (34.78%) (p < 0.05) groups. Compared with parallel CPA groups (G0 and G1), nonparallel CPA groups (G2 and G3) exhibited greater disc height (DH) reduction (ΔDH range 3.1-3.4 mm vs 1.4-2.0 mm, p < 0.05), higher cage stress (range 55.50-57.29 MPa vs 53.45-54.96 MPa), increased displacement (range 73.62-78.28 × 10-2 mm vs 72.21-72.37 × 10-2 mm), and elevated range of motion (ROM) in flexion. Clinical scores (visual analog scale and Oswestry Disability Index) were not different between groups.

CONCLUSIONS OLIF-AF with parallel screw placement in the coronal plane (G0 and G1) reduced CS risk and enhanced biomechanical stability by minimizing cage stress, displacement, and ROM. Horizontal screw bifurcation (G1 vs G0) did not demonstrate a statistically significant association with CS risk. Furthermore, there were no significant differences in fusion rates or clinical outcome measurements at different angles of AF.