Impact of Expandable Versus Static Interbody Cages on Subsidence and Outcomes in Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Systematic Review and Meta-Analysis Publisher



Shehniamirkhan M ; Paeinmahali A ; Bagherzadeh S ; Safari Dehnavi N ; Roohollahi F ; Kim P ; Alikhani P ; Rostami M
Source: Global Spine Journal Published:2026

Abstract

Study Design: Systematic review and meta-analysis. Objective: To compare expandable and static interbody cages in MIS-TLIF with respect to subsidence, radiographic outcomes, fusion rates, and patient-reported outcomes. Methods: Following PRISMA 2020 guidelines and a preregistered PROSPERO protocol, we searched PubMed/MEDLINE, Embase, Scopus, Web of Science, the Cochrane Library, and OVID through December 2025. Studies reporting clinical or radiographic outcomes of MIS-TLIF using expandable or static cages were included. Random-effects meta-analyses were performed, and risk of bias was assessed using Joanna Briggs Institute tools. Results: Twenty-three studies encompassing 1838 patients and 2074 fused levels met inclusion criteria. Expandable cages demonstrated a lower pooled subsidence rate than static cages (12.8% vs 25.7%), representing roughly a 50% relative reduction. When subsidence occurred, its magnitude was similar between groups (5.33 mm vs 4.54 mm). Improvements in VAS back pain (4.27 vs 4.29), VAS leg pain (3.80 vs 4.28), and ODI (20.16 vs 28.29) were comparable. Sensitivity analyses limited to low-risk studies showed consistent trends, although Egger’s regression suggested possible small-study effects for subsidence. Conclusions: In MIS-TLIF, expandable cages are associated with lower subsidence rates while achieving radiographic and clinical outcomes similar to static cages. However, only three studies directly compared the two cage types; the synthesis largely relies on indirect comparisons is susceptible to confounding. These findings should not be regarded as evidence of a causal effect of cage design. © The Author(s) 2026. This article is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 License (https://creativecommons.org/licenses/by-nc-nd/4.0/) which permits non-commercial use, reproduction and distribution of the work as published without adaptation or alteration, without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage).