Comparative Clinical and Radiological Outcomes of Banana-Shaped Versus Straight Cages in Biportal Endoscopic Transforaminal Lumbar Interbody Fusion: A Retrospective Cohort Study

Objective: This study aims to evaluate and compare the clinical and radiological outcomes of biportal endoscopic transforaminal lumbar interbody fusion (BE-TLIF) using banana-shaped versus straight interbody cages. BE-TLIF has emerged as a minimally invasive technique for treating lumbar spondylolisthesis. Banana-shaped and straight cages are the most commonly used cage types in BE-TLIF; however, their relative clinical and radiological outcomes remain unclear.Methods: This retrospective cohort study included 34 patients undergoing single-level BE-TLIF from January 2023 to May 2024. Seventeen patients received banana-shaped cages (group A) and 17 received straight cages (group B). Radiological assessments included disc height (DH), segmental lordosis angle (SLA), lumbar lordosis angle, cage position, and subsidence. Clinical outcomes were evaluated using the visual analogue scale (VAS) for back and leg pain and the Oswestry Disability Index (ODI). Fusion status was evaluated at 12 months postoperatively using computed tomography according to the modified Bridwell grading system.Results: Both groups demonstrated significant postoperative improvements in VAS and ODI scores, with no statistically significant differences between the groups. Radiological outcomes, including restoration of DH and SLA, were slightly better in the banana-shaped cage group, but this difference did not reach statistical significance. Straight cages were more often placed anteriorly, whereas banana-shaped cages tended to occupy the midlateral position. Fusion rates were comparable (100% vs. 94.1%, p>0.05), and subsidence occurred in 23.5% of cases in both groups.Conclusion: Despite differences in cage positioning, banana-shaped and straight cages yielded comparable clinical and radiological outcomes in BE-TLIF. Either cage type can be effectively utilized in BE-TLIF, providing flexibility in surgical planning, particularly in resource-limited settings.