OUTCOME MEASURES The levels of inflammatory cytokines interleukin-1 beta (IL-1ß), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-a) were quantified in muscle tissue directly anterior to the index level based on the intensity of fluorescence in each slide. The large animal model included two instrumented levels with one level implanted with a PEEK interbody cervical cage and the alternate level implanted with a PEEK zeolite composite interbody device. STUDY DESIGN/SETTING In vitro cell culture study in combination with a large animal functional cervical spine model. Similarly, the immune response measured at the local sites in a large animal study was also studied in order to determine the inflammatory response at the local implanted site. PURPOSE The objective of this study was to compare the activation state of macrophages, as determined by selected gene and protein expression profiles, following in vitro exposure to PEEK zeolite and PEEK based spinal interbody devices. It was hypothesized that IL-1ß, IL-6, and TNF-a cytokine expression levels results would be different for PEEK and a novel zeolite filled PEEK composite (ZFuze, DiFusion Technologies). The combination of results from three separate kinds of studies would potentially weave a better understanding of PEEK fibrous encapsulation around retrieved implanted PEEK devices. The cell studies in combination with larger animal studies help understand the importance of appropriate choice in materials. Studies involving macrophages facilitate the understanding behind the mechanism of fibrous capsule formation anecdotally reported with PEEK implants. Based on the current understanding of the immune system, both the innate and adaptive components, a combination of tests on current design materials in spinal implant devices may help understand potential clinical complications and thus reduce the potential adverse events associated with specific design materials. BACKGROUND CONTEXT Osteoimmunology, the study of the relationship between the musculoskeletal system and immune system, has emerged as an important consideration in biomaterial research.

Difusion zfuse