3D Printed Silicon Nitride Porous PEEK Composite Spinal Cages for Anti-Infection - PROJECT SUMMARY—When neck and back pain becomes intractable, spinal fusion is the gold-standard
treatment. However, up to 12% of these fusions fail due to infection, resulting in substantial personal and financial
costs. In most cases, these infections are associated with the hardware used to stabilize the fusion. Traditionally
molded or machined polyether ether ketone (PEEK) cages are widely used for this purpose due to PEEK’s
strength, elastic modulus comparable to bone, biocompatibility, and radiolucency. However, traditional PEEK
cages and common alternatives are prone to spinal infection. Silicon nitride (Si3N4) spacers have been used in
other spinal applications with an excellent antimicrobial performance history (i.e., only 0.006% of implants have
been associated with infection), and they provide superior osseointegration compared to other materials.
Unfortunately, Si3N4 is not ideal for stabilizing spinal fusions because the material may be susceptible to
subsidence and brittle fracture. In this Phase I STTR, SINTX Technologies, in collaboration with Drexel University
and Thomas Jefferson University, will combine the antimicrobial and osseointegrative properties of Si3N4 with
the strength and elasticity of PEEK to develop novel 3-D-printed antimicrobial cervical cages. Development and
commercialization of a 3DP Si3N4-PEEK cervical cage would address a critical unmet clinical need for an
antimicrobial spinal fusion stabilizer that promotes osseointegration, withstands in vivo loading, and facilitates
imaging. Aim 1. Design a 3DP Si3N4-PEEK cervical cage that meets the static loading requirements of ASTM
F2077. Milestone: Demonstrate static compression, shear, and torsion strength of 3DP Si3N4-PEEK’s porous
cages that meets or exceeds the guidelines for cervical cages established by ASTM F2077 and benchmarked
for many cage manufacturers in the literature. Aim 2. Determine antibacterial activity and osteoblast
proliferation/maturation as a function of Si3N4 percentage. Milestone: A >1.5 log reduction in bacterial
colonization while retaining osteoblastic proliferation/maturation. Impact—This project is expected to
demonstrate the feasibility of creating cervical cages that simultaneously retain the superior radiological and
biomechanical qualities of 3DP PEEK biomaterials while preserving the osseointegrative and antimicrobial
qualities of Si3N4. A Phase II STTR or SBIR would advance the 3DP Si3N4-PEEK cervical cage to IDE-enabling
studies, including assessments of fatigue performance, subsidence resistance, and preclinical performance in a
full-scale rigorously powered in vivo model. Rationally designed antibacterial spinal cages that reliably reduce
infection are critical, especially given the personal and financial costs of failed fusions as well as the increasing
numbers of spinal fusions in the US due to our aging population. Milestone for Progression to Phase II—
Delivery of a 3DP Si3N4-PEEK cervical cage that (1) meets the static loading requirements of ASTM F2077, (2)
meets minimum performance thresholds for osseointegration, and (3) meets minimum performance thresholds
for antibacterial activity. Quantitative targets are included in the Approach.
