Interbody material composition and bone morphogenetic protein-2—risks and benefits of utilization: a narrative review

Background and Objective: Technological and methodological advancements have created a rapidly evolving landscape of interbody devices and materials available for spinal fusion. This includes advancements in implant design and materials. Further, the use of biologics to augment fusion in combination with these devices creates an additional layer of complexity for surgeons to navigate. This review will discuss current interbody cage material choices, their respective risks and benefits, the role of interbody devices in the cervical and lumbar spine, and the use of recombinant human bone morphogenic protein 2 (rhBMP-2). Methods: A search of the literature available on PubMed was performed in 2023. Search terms included interbody device, interbody materials, interbody fusion, rhBMP-2, and bone morphogenetic protein. Subsequent searches with the same terms were used during the review process. Key Content and Findings: There is a vast array of interbody devices and biologics available to spine surgeons. The most commonly used non-autologous materials include polyetheretherketone (PEEK), titanium, allograft (structural and non-structural), and mixed-material implants. Titanium devices tout the benefit of biocompatibility and bony in-growth, at the expense of a substantially higher elastic modulus and therefore risk of subsidence. PEEK devices are radiopaque with an elastic modulus similar to bone, though can produce pro-inflammatory reactions and are not inherently biocompatible. Allograft devices are also popular for improved visualization of fusion through follow up, though have a risk of resorption. Conclusions: There remains a lack of consensus on preferred interbody material. Many options are available, each with its own risks and benefits, and surgeons should be aware of these factors prior to implantation.