Spinopelvic parameters and functional outcomes following posterior lumbar interbody fusion with polyetheretherketone cage implantation for adult lumbar spondylolisthesis

Objectives: In the surgical treatment of lumbar spondylolisthesis (LS) with posterior lumbar interbody fusion (PLIF), interbody fusion cages play a vital role in supporting the vertebral body, restoring disc height, facilitating fusion, and correcting sagittal alignment. The objective of this study was to detect the effect of cage implantation on sagittal parameters and functional outcomes in patients undergoing PLIF surgery for LS. Methods: This retrospective cohort study included 120 patients who had undergone open PLIF surgery. Radiological outcome was evaluated using plain radiographs postoperatively and at 6 weeks, 3 months, 6 months, and 2 years. Functional outcome was assessed using the Visual Analog Scale (VAS) and the Oswestry Disability Index (ODI) pre- and postoperatively. Results: This study included 120 patients (mean age 49.9 ± 7.0 years; 60.8% female; all single-level procedures: L4–L5 in 45.8%, L3–L4 in 27.5%, L5–S1 in 21.7%, and L2–L3 in 5.0%). Degenerative LS accounted for 63.3% of cases and isthmic LS for 36.7%. Mean operative time was 100.1 ± 18.0 min and mean blood loss was 493.5 ± 72.0 mL. The overall complication rate was 6.7% (8/120), with a reoperation rate of 1.7% (2/120). Satisfactory fusion (Bridwell grades I–II) was achieved in 86.7% of cases. The mean pre-operative ODI was 69.9 ± 6.2% and decreased significantly to 22.7 ± 4.5% at 2 years ( p < 0.001; minimal clinically important difference met in 100%). The mean pre-operative VAS was 7.9 ± 0.6 and decreased significantly to 3.9 ± 0.5 ( p < 0.001). Lumbar lordosis (LL) improved from 37.7 ± 5.0° to 54.2 ± 4.2° and pelvic incidence–LL mismatch decreased from 21.1 ± 5.3° to 4.8 ± 2.6° (both p < 0.001). The mean pre-operative sacral slope was 24.73, which increased significantly to 35.9 postoperatively. The mean pre-operative pelvic tilt was 34.73, which significantly decreased postoperatively to 22.77. The mean pre-operative pelvic incidence was 59.1, which did not significantly decrease to 59.07 postoperatively. The mean pre-operative LL was 37.7°, which increased significantly postoperatively to 54.17. Conclusion: The use of a cage in PLIF significantly enhances mechanical stability, fusion success, and functional recovery in adult LS.