Improved Clinical and Radiological Outcomes with Double-Cage Biportal Endoscopic Transforaminal Lumbar Interbody Fusion: A Comparative CT-Based Study

<b>Background/Objectives</b>: When transitioning from an older surgical technique to a newer one, we expect improved treatment outcomes and fewer complications. However, direct comparative studies to confirm these advantages are often lacking. Tubular minimally invasive transforaminal lumbar interbody fusion (MISTLIF) has been widely used, but limitations in visualization and endplate preparation may compromise fusion quality. Biportal endoscopic TLIF (BETLIF), a more recent alternative, offers enhanced magnification and superior hemostasis. Still, CT-based comparative data on fusion integrity remain limited. To evaluate the clinical and radiological outcomes following a chronological transition from MISTLIF to BETLIF, using thin-slice CT to assess fusion integrity. <b>Methods</b>: This retrospective study analyzed 179 patients treated by a single surgeon between January 2018 and May 2021. The first 90 cases underwent MISTLIF, followed by 89 BETLIF procedures. Clinical outcomes included Visual Analog Scale (VAS), Oswestry Disability Index (ODI), and Japanese Orthopedic Association (JOA) scores. Radiological assessments at one year postoperatively (X-ray and thin-slice CT) included disc height, segmental lordosis, Bridwell fusion grade, cage subsidence, and subchondral osteolysis. <b>Results</b>: BETLIF was associated with significantly shorter hospital stays (5.7 vs. 7.4 days) and fewer transfusions (0% vs. 14.7%). BETLIF showed significantly better ODI (12.7 vs. 23.5), JOA scores (26.4 vs. 20.6), and comparable VAS improvement. Radiologically, BETLIF had significantly higher fusion rates (93.3% vs. 82.4%), greater disc height restoration, and lower rates of cage subsidence (5.0% vs. 13.7%) and osteolysis (13.3% vs. 52.9%). <b>Conclusions</b>: BETLIF demonstrated superior clinical and radiological outcomes, likely due to enhanced endoscopic visualization and precise endplate preparation.