Host Bone Response to Polyetheretherketone Versus Porous Tantalum Implants for Cervical Spinal Fusion in a Goat Model

Study Design. In vivo assessment of polyetheretherketone (PEEK) and porous tantalum (TM) cervical interbody fusion devices in a goat model. Objective. Directly compare host bone response to PEEK and TM devices used for cervical interbody fusion. Summary of Background Data. PEEK devices are widely used for anterior cervical discectomy and fusion but are nonporous and have limited surface area for bone attachment. Methods. Twenty-five goats underwent single-level anterior cervical discectomy and fusion and were alternately implanted with TM (n = 13) or PEEK devices (n = 12) for 6, 12, and 26 weeks. Both devices contained a center graft hole (GH), filled with autograft bone from the animal's own iliac crest. The percentage of bone tissue around the implant, percentage of the implant surface in direct apposition with the host bone, and evidence of bone bridging through the implant GH were assessed by using backscattered electron imaging. Bone matrix mineral apposition rate was determined through fluorochrome double labeling, and sections were stained for histological analysis. Results. The TM-implanted animals had significantly greater volumes of bone tissue at the implant interface than the PEEK animals at all-time points. The TM animals also had a significantly greater average mineral apposition rate in the GH region at 6 and 12 weeks than the PEEK animals. No difference was observed at 26 weeks. A greater number of TM-implanted animals demonstrated connection between the autograft bone and both vertebrae compared with the PEEK implants. Histological staining also showed that the TM devices elicited improved host bone attachment over the PEEK implants. Conclusion. The TM implants supported bone growth into and around the implant margins better than the PEEK devices. TM's open cell porous structure facilitated host bone ingrowth and bone bridging through the device, which could be beneficial for long-term mechanical attachment and support in clinical applications.