Expandable Cage in Minimally Invasive Transforaminal Lumbar Interbody Fusion: Comparative Data with Static Cage from a Single Institution and a Single Surgeon

Abstract

Background: Minimally invasive surgery-transforaminal lumbar interbody fusion (MIS-TLIF) is widely adopted for the treatment of lumbar degenerative disease. Expandable cages are now increasingly used in MIS-TLIF to facilitate disc height restoration in narrow spaces. Despite theoretical advantages, the clinical and radiologic outcomes of expandable cage compared to static cage remain controversial.

Methods: This retrospective study analyzed 151 patients who underwent single-level lumbar MIS-TLIF performed by a single surgeon at a single institution, with more than 1-year follow-up. Static cages were exclusively used from May 2022 to March 2023 (n = 76), and expandable cages from April 2023 to March 2024 (n = 75). The primary outcomes were radiological disc height and lordotic angles.

Results: The expandable cage group demonstrated significantly greater postoperative disc height restoration compared to the static cage group at both immediate postoperative periods (10.3 ± 1.2 mm vs. 9.5 ± 1.5 mm, P = 0.003) and at 1-year follow-ups (9.6 ± 1.4 mm vs. 9.0 ± 1.6 mm, P = 0.028). There were no significant differences between the groups in lordotic angles, fusion rates, and clinical outcomes. Various complications were also comparable, other than the incidence of cage subsidence > 3 mm, which was higher in the expandable cage group (14.7% vs. 3.9%, P = 0.047).

Conclusions: Expandable cages in MIS-TLIF demonstrated superior disc height restoration compared to static cages, which were maintained throughout a 1-year follow-up period despite the relatively higher subsidence rate. No significant differences were observed in terms of lordotic angle restoration, clinical outcomes, or fusion rates.