Spine Interbody Fusion Cages: Concepts, Design Trends, and Emerging Personalized Solutions

Background/Objectives: Interbody fusion cages provide both structural support and a biologically favorable environment for osseointegration. Through recent decades, cage design and biomaterial selection have evolved to more adapted implants in different concept philosophies. Based on this development, the objective of this work was to develop a systematic review of the state of the art regarding spine interbody cage concepts on the market and anticipate future directions in cage design. Methods: A systematic review following PRISMA 2020 guidelines was conducted in three databases of reference, Scopus, PubMed and Mendeley, in September 2025, considering results from between 2015 and the present using the following keywords: spine, interbody, cage and concept. A revision of the first results was performed, and duplicate entries were excluded, as well as papers without a firm relevance for cage design concepts. Results: This search resulted in 76 selected papers and different design concepts and clinical outputs, and after a duplicate analysis, just 40 papers were selected. The material properties may play an important role in the characteristics of the implant and critically influence load-sharing and bone ingrowth. Surface modifications, including texturing, porosity engineering, and osteoconductive coatings, have been introduced to enhance cellular adhesion and fusion rates. It was observed through the research performed that the main problems are related to micromobility, implant displacement and stress shielding effects in adjacent vertebras. Conclusions: Among the different evolutions observed in cages through the years, design changes played an important role in adapting each case. Knowing that the design could be strongly influenced by the surgical approach used (anterior, posterior, transforaminal or lateral) and bone quality, it is also possible to find, nowadays, different options for different needs that are only accessible due to the technological advances in additive manufacturing, which allowed the development of patient-specific implants.