Biportal Endoscopic TLIF With an Expandable Cage: Technical Note and Preliminary Results in Terms of Segmental Lordosis Achievement and Disc Height Elevation.

Background: Biportal endoscopic transforaminal lumbar interbody fusion (BE-TLIF) is a minimally invasive TLIF (MIS-TLIF) technique, commonly performed with various cage types. Expandable cages are particularly effective in achieving segmental lordosis (SL) and disc height (DH) elevation in minimally invasive TLIF. However, the published literature lacks details regarding how these outcomes can be accomplished using BE-TLIF with an expandable cage.

Methods: Nine cases (10 levels) of BE-TLIF with an expandable cage were reviewed. Procedures including unilateral laminotomy and bilateral decompression, cage expansion trials, and bilateral facetectomies were carried out under biportal endoscopy to achieve SL and DH elevation. Postoperative standing x-ray images at 3 months and reconstructed computed tomography images were analyzed. The sublaminar decompression angle-measured as the angle between the spinous process and the sublaminar decompression line on axial computed tomography-was used to evaluate contralateral sublaminar decompression.

Results: All procedures were completed without changes to the surgical methods. Eight patients underwent single-level fusion, with 4 of them receiving additional decompression at adjacent levels. One patient underwent a 2-level fusion. Four cases utilized 12° lordotic cages, while the rest employed 20° hyperlordotic cages. The total time for each fusion was 152.5 ± 38.5 minutes. Segmental lordosis increased by 5.1°, with anterior and posterior DH elevations of 4.8 ± 1.7 mm and 3.1 ± 1.8 mm, respectively. No endplate injuries or early cage subsidence occurred. The mean sublaminar decompression angle was 31.8° ± 7.0°.

Conclusions: BE-TLIF with an expandable cage may offer benefits in SL correction and DH elevation. These advantages are attributed to the use of more lordotic expandable cages, combined with contralateral facetectomies and careful endplate preparation-key features of the BE-TLIF technique.

Clinical relevance: SL correction and DH elevation can be achieved through BE-TLIF, which helps to reduce the recurrence of symptoms and improves the lumbar lordotic curve.

Level of evidence: 4: