Sagittal Alignment and Clinical Outcomes After Biportal Endoscopic Transforaminal Lumbar Interbody Fusion Using a Single Expandable Cage: One Year Follow-up

Abstract

OBJECTIVE: Advancements in expandable cage technology may overcome limitations, such as narrow working corridor, continuous irrigation, and endplate injury risk in biportal endoscopic transforaminal lumbar interbody fusion (BE-TLIF). We evaluate sagittal realignment, fusion rates, and clinical outcomes over 1 year using a single bullet-type expandable cage. square METHODS: This retrospective study included 29 patients (38 levels) who underwent BE-TLIF with a single expandable cage and were followed for at least 12 months. Radiological assessments included disc height (DH), segmental lordosis (SL), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), PI-LL mismatch, and cage subsidence. Clinical outcomes were evaluated using back and leg Visual Analog Scale (VAS), Oswestry Disability Index (ODI), 36-Item Short Form Survey (SF-36), and EuroQol-5 Dimension (EQ-5D). Fusion was evaluated using CT based Bridwell classification at 6 and 12 months. square RESULTS: At 12 months, the fusion rate was 92.1%, with significant subsidence (>= 2 mm) in 3 levels. Anterior and posterior DH increased by 3.97 and 4.22 mm, while SL and LL improved by 3.01 degrees and 5.00 degrees, respectively. Back and leg VAS and ODI decreased by 3.0, 5.0, and 12.76 points, while EQ-5D increased by 5.81 points. Greater PI-LL correction correlated with higher fusion rates and better functional recovery. Patients with preoperative sagittal malalignment showed significant improvements. Cage size and type had limited effect on outcomes. square CONCLUSIONS: BE-TLIF using a single bullet-type expandable cage achieved favorable outcomes at 1 year, with meaningful sagittal correction and fusion rates, supporting the non-inferiority of this construct in short-segment lumbar fusion.