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

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.