Development and Pre-Clinical Testing of Antimicrobial PEKK/Silicon Nitride Trauma Plates with Carbon Fiber Reinforcement

PROJECT SUMMARY—More than 2 million Americans are hospitalized each year with bone fractures, and
many more undergo outpatient procedures for fracture reduction and fixation. Some injuries can be treated with
closed reduction and splinting or casting to immobilize the bone during healing. However, at some sites, more
than half of fractures require open reduction and internal fixation. Despite advances in implant materials, implant-
associated infections remain a challenge. Depending on the location of the fracture, characteristics of the injury
(e.g., open vs. closed fracture), and characteristics of the patient (e.g., presence of diabetes or other
comorbidities), between 1% and 30% of fixation sites are compromised by device-associated infections. For
example, lower extremity fractures requiring internal fixation are associated with high infection rates that impede
bone healing, increase the risk of long-term disability, and increase the cost and complexity of patient care.
Further advances in fixation device materials are needed to reduce the incidence of device-associated infections
and improve patient outcomes. In this Phase I STTR, SINTX Technologies seeks to demonstrate proof-of-
concept for a novel antimicrobial material that could be used to produce a broad range of internal fixation
devices for fracture repair. Trauma plates are the most widely used internal fixation devices in trauma
applications. Plates are typically crafted from metal, molded carbon fiber reinforced (CFR) polyetheretherketone
(PEEK) composites, or CFR-polyetherketoneketone (CFR-PEKK). Unfortunately, devices made from all of these
materials are prone to infection. SINTX pioneered the use of silicon nitride (Si3N4) implants that have inherent
antimicrobial activity and have achieved an excellent anti-infective profile in clinical use (i.e., only 0.006% of
implants have been associated with infection). Although Si3N4 has excellent antimicrobial properties, it is
susceptible to brittle fracture and therefore not suitable for stabilizing fractures. In this Phase I STTR, SINTX and
its collaborators propose to use a proprietary process to embed microscopic Si3N4 powder into the surface of
CFR-PEKK and evaluate this novel material’s performance as an antimicrobial material for fixation devices.
Trauma plates will serve as a prototype for proof-of-concept, with the goals of a) advancing a Si3N4-CFR-PEKK
trauma plate for further development and commercialization and b) demonstrating the potential for the material
to be used in other fixation devices that must withstand in vivo loading, facilitate imaging, and resist infection.
Aim 1. Design an α-Si3N4 -CFR-PEKK trauma plate that meets or exceeds requirements for static and
fatigue bending strength. Aim 1 Milestone: Design and develop a Si3N4-coated CFR- PEKK trauma plate that
preserves at least 90% of static and fatigue bending strength of uncoated trauma plates in accordance with
ASTM F382, D7264, D790-10. Aim 2. Characterize antibacterial activity and biocompatibility as a function
of α-Si3N4 percentage. Aim 2 Milestone: A andgt; 2 log reduction in bacterial colonization while retaining osteoblastic
proliferation/maturation.PROJECT NARRATIVEImplantable devices used to repair bones following trauma can introduce or promote bacterial infection that
delays healing and can cause other complications. This project is designed to advance the development of a
new composite material for implantable bone repair devices by embedding antibacterial alpha silicon nitride into
the surface of a commonly used carbon fiber reinforced plastic. Surgical use of this new material is expected to
reduce the risk of infection in bone repair and prevent the device from becoming a source or reservoir of infection.