Strategic Use of the 30-Degree Endoscope in Biportal Endoscopic Lumbar Interbody Fusion for Spondylolisthesis With Severe Disc Height Loss: A Technique Note and Case Series

<sec><title>Background</title> To evaluate the clinical and radiological outcomes of biportal endoscopic lumbar interbody fusion (BE-LIF) using the 30-degree endoscope in patients with lumbar spondylolisthesis and severe disc height loss and to highlight its technical advantages in endplate preparation and contralateral decompression. </sec><sec><title>Methods</title> This retrospective study included 21 patients with single-level Meyerding grade II spondylolisthesis and preoperative disc height <5 mm who underwent BE-LIF combined with percutaneous pedicle screw fixation between February 2023 and February 2025. Clinical outcomes were assessed using the visual analog scale for back and leg pain and the Oswestry Disability Index. Radiographic parameters, including vertebral slip, disc height, and foraminal height, were evaluated on standing lateral x-ray images, while fusion status was assessed using Bridwell grading on 6-month postoperative computed tomography scans. </sec><sec><title>Results</title> At a mean follow-up of 11.7 ± 2.6 months, all patients demonstrated statistically significant clinical improvement, visual analog scale scores decreased from 7.2 ± 0.6 to 1.5 ± 0.5 for low back pain, from 7.5 ± 0.5 to 1.7 ± 0.6 for leg pain, and the Oswestry Disability Index improved from 42.6 ± 5.7 to 15.7 ± 2.5 (<italic>P</italic> < 0.001). Radiologically, vertebral slip was reduced from 11.3 ± 1.5 mm to 2.1 ± 0.4 mm. Anterior and posterior disc heights increased from 5.6 ± 0.6 mm and 4.9 ± 0.5 mm to 8.5 ± 1.2 mm and 8.3 ± 1.4 mm, respectively. Foraminal height improved from 9.8 ± 1.7 mm to 14.7 ± 2.8 mm. Fusion was confirmed in all cases (Bridwell grade I: 28.6%, grade II: 71.4%), with no cage subsidence or major complications reported. </sec><sec><title>Conclusion</title> The use of the 30-degree endoscope in BE-LIF for spondylolisthesis with severe disc collapse provides enhanced visualization, facilitates safe and effective decompression, and results in favorable clinical and radiological outcomes. </sec><sec><title>Level of Evidence</title> 3. </sec>