Expandable cage technology in minimally invasive transforaminal interbody fusion: where are we and what does the future hold?

Introduction: Expandable cages are designed to address the limitations of static cages in minimally invasive transforaminal lumbar interbody fusion (MI-TLIF). These devices enable collapsed insertion with in-situ expansion, aiming to restore disc height and lordosis, indirect foraminal decompression, and sagittal alignment with reduced neural and tissue trauma. Advancements in bi-dimensional cage expansion, endplate interaction, and innovative materials have been designed in attempt to improve fusion rates and clinicoradiographic outcomes.

Areas covered: This review examines the structural design and mechanisms of expandable interbody cages, their clinical outcomes compared to static cages, and their limitations, including subsidence and cost. PubMed, Scopus, and Google Scholar were reviewed for relevant literature published up until November, 2024. We also discuss emerging technologies, such as bi-planar expansion cage technology and patient-specific implants, and their potential to optimize fusion procedures.

Expert opinion: Expandable cages offer clear benefits for MI-TLIF, mainly restoring disc height and minimizing insertion-related risks. Innovations like bi-planar and patient-specific designs help address limitations, but cost and long-term outcomes remain concerns. These devices can improve fusion outcomes, especially in degenerative or deformity cases.