Martin J. Petrak P.Eng, President, CEO, Precision ADM / Orthopaedic Innovation Centre
Trevor C. Gascoyne P.Eng, Clinical Research Manager, Orthopaedic Innovation Centre
Biocompatible materials; polycarbonate (PC-ISO), polylactic acid (PLA) and polycaprolactone (PCL) were combined with three heat-stable antibiotics; gentamicin, tobramycin, and vancomycin, to produce 1%, 2%, and 5% concentrations (by mass). Proof-of-concept testing began with zone of microbial inhibition (ZoI) testing (Kirby-Bauer disk diffusion), for which fused deposition modeling (FDM) and selective laser sintering (SLS) processes were used to create a series of test coupons. FDM was used to produce tensile and compressive test samples of PC-ISO, PLA, and PCL at 1% antibiotic concentration for basic mechanical testing. A second set of samples were produced and exposed to hydrogen peroxide vapor sterilization prior to testing to elucidate any ill effects of sterilization. Finally, material wear resistance consisted of pin-on-disc testing of PC-ISO, PLA, and PCL at 1% antibiotic concentration for a total of 1.32 million cycles per material.
ZoI results were significant with all concentrations of antibiotics inhibiting bacterial growth (with exception of PLA-vancomycin) with SLS samples outperforming FDM samples. Mechanical and pin-on-disk testing indicate the viability of all of these materials as temporary antibiotic-infused implants in revision hip or knee replacement. Testing to industry standards aided in the development of the materials, particularly how AM influences material properties and application-specific behavior.