#294 Decreased Bacterial Biofilm Formation and Function Associated with Silicon Nitride (Si3N4) Materials Used in Interbody Fusion Cages (IBF) Compared to Titanium and Polyetheretherketone (PEEK)

Oral Posters: Lumbar

Presented by: D. Orndorff

Author(s):

D. Gorth (1)
S. Puckett (2)
B. Ercan (1)
T.J. Webster (1)
A.A. Patel (2)
R. Lakshminarayanan (3)
J.A. Youssef (4)
D. Orndorff (4)

(1) Brown University, School of Engineering and Department of Orthopaedics, Providence, RI, USA
(2) Loyola University School of Medicine, Chicago, IL, USA
(3) Amedica Corporation, Salt Lake City, UT, USA
(4) Durango Orthopedic Associates/Spine Colorado, Durango, CO, USA

Abstract

Background: Infection has been reported on an array of implantable devices including orthopedic joint prosthetics and spinal implants. Moreover, the risk of infection is increasing due to the emergence of antibiotic resistance and the quick speed at which bacteria penetrate wounds developing biofilms on implants. There is, therefore, a significant interest in the development of orthopedic implant materials that inhibit bacteria functions without the use of antibiotics.

Purpose: To quantify the inhibitory effects of a novel silicon nitride biomaterial, used in interbody fusion cages (IBF), on bacterial function.

Study Design: In vitro, inoculation.

Outcome Measures: Bacterial biofilm production, Bacterial count

Methods: This in vitro study tested bacterial (S. aureus, S. epidermidis, and P. aeruginosa) growth for up to 72 hours on three materials frequently used in the spine: titanium, polyetheretherketone (PEEK), and Si3N4 (Silicon Nitride). Bacterial growth was quantified by 1) Crystal violet which stains biofilm presence and 2) Live bacterial counts per high-powered field.

Results: Crystal violet staining demonstrated significantly less biofilm production and lower bacterial counts on Si3N4 samples compared to PEEK (p < 0.01) and titanium samples (p < 0.01) after 72 hours. Decreases in biofilm production were identified for all bacterial strains. S. epidermidis, S. aureus, and P. aeruginosa biofilm production was over 4, 5, and 10 times less on Si3N4 than PEEK and titanium, respectively, after 72 hours. Moreover, the number of live S. epidermidis decreased over 10 times from 105 to 104colony forming units on Si3N4 compared to both titanium and PEEK after 72 hours. The number of live S. aureus decreased by over a half from 105 to 5x104 colony forming units on Si3N4 compared to both titanium and PEEK after 72 hours. Lastly, the number of live P. aeruginosa decreased by over 10 times from 106 to 105colony forming units on Si3N4 compared to both titanium and PEEK after 72 hours.

Conclusions: This study provides initial evidence that Si3N4 is a novel antibacterial orthopaedic implant material that may decrease bacterial function, specifically biofilm formation and bacterial counts, without resorting to the use of antibiotics.