3D Printed Silicon Nitride Porous PEEK Composite Spinal Cages for Anti-Infection

PROJECT SUMMARY Spinal fusion is the standard treatment for persistent neck and back pain, but the hardware used to stabilize the fusion can harbor or even promote bacteria that lead to persistent, difficult-to-treat infections that are costly and damaging to patient health. Among the available materials for spinal fusion, polyether-ether-ketone (PEEK) cages stand out due to their strength, biocompatibility, and radiolucency, but like other materials, they are susceptible to spinal infections. Silicon nitride (Si3N4) spacers have been used in other spinal applications where their rates of reportable adverse events due to infection are much lower than industry norms, but they are not ideal for stabilizing spinal fusions due to their potential for subsidence and brittle fracture. To address this challenge, SINTX used Phase I SBIR funding to develop and test a 3D-printed Si3N4-PEEK material that incorporates the antimicrobial and osseointegrative properties of Si3N4 with the strength and elasticity of PEEK. In this Phase II SBIR, SINTX proposes to use this material to develop a 3D-printed anti-microbial spinal fusion cage that promotes osseointegration, withstands in vivo loading, and facilitates imaging. The project includes long-term biomechanical performance and in vivo fusion property testing in both normal and contaminated operative scenarios. Successful completion of these activities will position SINTX to prepare a 510(k) premarket notification application for FDA. SINTX anticipates further development and commercialization of a 3D-printed Si3N4-PEEK spinal fusion cage will provide orthopedic surgeons a high-performance fusion device that could greatly reduce the incidence of fusion-associated infections. Aim 1. Minimize potential design and manufacturing hazards by formal design and process risk management analyses in accordance with ISO 14971. Milestone: Completion of the design FMEA and process FMEA per ISO 14971 to minimize risks associated with the novel cervical cages and design freeze. Aim 2. Verify that the finalized 3DP Si3N4-PEEK cervical cage meets the static and fatigue loading requirements of ASTM F2077 and subsidence requirements of ASTM F2267. Milestone: Following the design freeze in Aim 1, demonstrate static and fatigue compression, shear, and torsion strength and subsidence resistance of the finalized 3DP Si3N4-PEEK’s porous cage meets or exceeds the guidelines for cervical cages established by ASTM F2077 and ASTM F2267 and benchmarked for many cage manufacturers in the literature. Aim 3. Determine antimicrobial activity (experimental arm) and in vivo biocompatibility and osteointegration (biocompatibility GLP arm) for a 3DP Si3N4-PEEK cervical cage in a caprine model of cervical spinal fusion. Milestone: Final, packaged, and validated implants will pass requirements in ISO 10993. 3DP Si3N4-PEEK implants will have biocompatibility, bone ingrowth, fusion, and resistance to infection comparable to or better than control 3DP PEEK spinal cages.