A Novel Switching Portal Technique in Biportal Endoscopic Transforaminal Lumbar Interbody Fusion: Technical Notes and Comparative Outcomes

Abstract

Objective: The use of a fixed portal arrangement during biportal endoscopic transforaminal lumbar interbody fusion (BE-TLIF) may result in suboptimal instrument trajectory angles, leading to inadequate endplate preparation or difficulties in cage implantation. Therefore, we propose the switching portal technique, which enables the operator to switch the viewing and instrument portals. The aim of this study is to describe our surgical technique and present comparative outcomes.

Methods: This study included 74 consecutive patients who underwent BE-TLIF at a total of 82 levels between January 2021 and July 2023 and were followed for at least 1 year after surgery. Patients were divided into two groups, the fixed portal group and the switching portal group, according to whether the switching portal technique was used for endplate preparation and insertion trajectory adjustment. Clinical and radiographical outcomes were analyzed between the two groups.

Results: Endplate injuries were significantly more common in the fixed portal group than in the switching portal group. The modified McNab's criteria were not significantly different between the groups, but the switching portal group had a greater proportion of excellent and good outcomes (92.3%) than the fixed portal group did (82.9%). Cage subsidence occurred in 20.5% of patients in the fixed portal group and 4.7% in the switching portal group.

Conclusions: The switching portal technique is safe and useful in BE-TLIF, as it enables effective disc preparation and ensures a precise trajectory for cage insertion, thereby significantly reducing the risks of endplate injury and cage subsidence.

Keywords: Biportal endoscopic spine surgery; Cage migration; Cage subsidence; Endplate injury; Switching portal technique; Transforaminal lumbar interbody fusion.