Antibacterial Optimization of Highly Deformed Titanium Alloys for Spinal Implants.

Katarzyna Kasperkiewicz,Łukasz Major,Roman Major,Anna Sypien,Adam Byrski,Marcin Dyner,Juergen M. Lackner,Magdalena Kopernik,Marcin Kot

doi:10.3390/molecules26113145

Abstract

The goal of the work was to develop materials dedicated to spine surgery that minimized the potential for infection originating from the transfer of bacteria during long surgeries. The bacteria form biofilms, causing implant loosening, pain and finally, a risk of paralysis for patients. Our strategy focused both on improvement of antibacterial properties against bacteria adhesion and on wear and corrosion resistance of tools for spine surgery. Further, a ~35% decrease in implant and tool dimensions was expected by introducing ultrahigh-strength titanium alloys for less-invasive surgeries. The tested materials, in the form of thin, multi-layered coatings, showed nanocrystalline microstructures. Performed direct-cytotoxicity studies (including lactate dehydrogenase activity measurement) showed that there was a low probability of adverse effects on surrounding SAOS-2 (Homo sapiens bone osteosarcoma) cells. The microbiological studies (e.g., ISO 22196 contact tests) showed that implanting Ag nanoparticles into Ti/TixN coatings inhibited the growth of E. coli and S. aureus cells and reduced their adhesion to the material surface. These findings suggest that Ag-nanoparticles present in implant coatings may potentially minimize infection risk and lower inherent stress.

Highlights

Orthopedic spine surgeries are highly challenging interventions with a high risk of neurological damage
In pediatrics, the focus is on the orthopedic stabilization of kyphosis and scoliosis, while fusions for osteoporotic vertebrae and spinal tumor resections dominate in the case of elderly patients
Low-vascularized sites around spinal implant surfaces are prone to surgical site infections (SSI) by Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Propionibacterium acnes

Summary

Introduction

Orthopedic spine surgeries are highly challenging interventions with a high risk of neurological damage. The main problems in all orthopedic spine surgeries with screw–rod–plate systems are bacterial surgical site infections (SSI), with rates up to 41.7% of surgeries in pediatrics (especially in myelodysplasia), resulting in patient morbidity, multiple operations and risks of paralysis. Immediate infection risks have been minimized by surgical techniques, but a reduction in delayed SSIs after a subclinical quiescent period is still a pressing need. They are generally diagnosed in late, highly intense stages. Bacterial adhesion and colonization on titanium implants form biofilms, in which adherent bacteria are protected from host defense systems and bactericidal agents [3,4,5]. Antimicrobial strategies must precede bacterial colonization and be introduced to the most endangered areas at high, but non-cytotoxic, doses

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