Radiographic and Clinical Trade-Offs Between Expandable and Polyetheretherketone Cages in Endoscopic Transforaminal Lumbar Interbody Fusion

Objective: To compare 1-year radiographic and clinical outcomes between expandable cages and polyetheretherketone (PEEK) cages in patients undergoing endoscopic transforaminal lumbar interbody fusion (TLIF).Methods: This retrospective, single-surgeon cohort study included 84 patients (32 expandable cage, 52 PEEK cage) with at least 1 year of radiographic and clinical follow-up. Radiographic parameters included disc height, foraminal height, segmental lordosis, subsidence, cage length, and the cage-to-vertebral body area ratio measured on computed tomography. Clinical outcomes were evaluated using Numerical Rating Scale (NRS) scores and Bridwell fusion grading. Group comparisons were performed using t-tests and chi-square tests, and multivariate regression analyses were conducted to identify independent predictors of subsidence and fusion.Results: PEEK cages demonstrated greater correction of segmental lordosis (2.6° vs -0.3°, p=0.003) and significantly lower total subsidence (2.2±1.7 mm vs. 4.6±2.4 mm, p=0.001) compared with expandable cages. In contrast, expandable cages were associated with significantly greater improvement in back pain at 1 year (β=1.71 NRS points, p=0.014). A larger cage-to-vertebral body area ratio independently reduced the risk of severe subsidence ≥5 mm (odds ratio, 0.34 per 0.1 increase; p=0.033). Fusion outcomes, defined as Bridwell grades 1–2, did not differ significantly between the 2 groups.Conclusion: Expandable cages provided greater back pain relief despite a higher degree of subsidence, whereas PEEK cages offered superior radiographic stability. These findings highlight important radiographic-clinical trade-offs in cage selection for endoscopic TLIF and support individualized decision-making based on patient anatomy, alignment objectives, and symptom profile.