Technical Feasibility and Early Clinical Outcome of Biportal Endoscopic Transforaminal Lumbar Interbody Fusion Using Larger Cage

BACKGROUND: Transforaminal lumbar interbody fusion with biportal endoscopic guidance (BE-TLIF) has been previously reported with promising clinical results. How-ever, complications such as delayed union or subsidence occurred as with open surgery. We assumed using larger cages would result in less occurrence of such complica-tions. We aimed to analyze the clinical outcome and technical feasibility of BE-TLIF using larger cages, initially designed for oblique lumbar interbody fusion. METHODS: We enrolled cases that underwent single-level BE-TLIF between January 2021 and January 2022. Polyetheretherketone cages that were larger than the conventional size were used. Diagnoses were degenera-tive spondylolisthesis or isthmic spondylolisthesis. Visual analog scale scores of the back and leg and Oswestry Disability Index were collected perioperatively. Modified Macnab criteria were used to evaluate the patients at the final follow-up. Radiologic outcome of interbody fusion rate and perioperative complications were analyzed.RESULTS: A total of 35 cases were included in this study. The mean age was 67.5 +/- 8.4 and consisted of 13 male patients, and the mean follow-up duration was 18.3 +/- 3.7 months. The majority (32/35, 91.3%) of the index level was located within the lower lumbar region, L4-S1. Oswestry Disability Index scores improved from 65.4 +/- 5.4 preoper-atively to 15.4 +/- 6.1 at the final follow-up (P< 0.001). Visual analog scale scores of the leg decreased from 7.9 +/- 1.5 to 1.7 +/- 1.5 at the final follow-up (P< 0.001). Per the modifiedMacnab criteria on the final follow-up, 94% of the patients reported good/excellent. Most (94.2%) of the patients showed fusion grade I and II at the 1-year follow-up. No patient showed subsidence or other postoperative complication.CONCLUSIONS: BE-TLIF using a larger cage was safely performed without risk of subsidence during the 1-year follow-up. A cage with a larger footprint may be advanta-geous in BE-TLIF in the aspect of interbody fusion and subsidence.