One of the most commonly identified pathogens responsible for orthopaedic implant infection is Staphylococcus epidermidis, which can form biofilms on surfaces. Currently, orthopaedic implants made of various surface materials are available, each with features influencing osseointegration, biocompatibility, and adherence of bacteria to the surface, which is the first step in biofilm formation. The aim of this experimental study was to investigate the effect of a high tribologic-resistant 2.5-µm zirconium nitride top coat on an antiallergic multilayer ceramic-covered cobalt-chromium-molybdenum surface on the formation of S. epidermidis biofilm compared with other commonly used smooth and rough orthopaedic implant surface materials.
(1) When evaluating the surfaces of a cobalt-chromium-molybdenum (CoCrMo) alloy with a zirconium (Zr) nitride coating, a CoCrMo alloy without a coating, titanium alloy, a titanium alloy with a corundum-blasted rough surface, and stainless steel with a corundum-blasted rough surface, does a Zr coating reduce the number of colony-forming units of S. epidermidis in an in vitro setting? (2) Is there quantitatively less biofilm surface area on Zr-coated surfaces than on the other surfaces tested in this in vitro model?
To determine bacterial adhesion, five different experimental implant surface discs were incubated separately with one of 31 different S. epidermidis strains each and subsequently sonicated. Twenty test strains were obtained from orthopaedic patients undergoing emergency hip prosthesis surgeries or revision of implant infection and 10 further strains were obtained from the skin of healthy individuals. Additionally, one reference strain, S. epidermidis DSM 3269, was tested. After serial dilutions, the number of bacteria was counted and expressed as colony-forming units (CFUs)/mL. For biofilm detection, discs were stained with 0.1% Safranin-O for 15 minutes, photographed, and analyzed with computer imaging software.
The lowest bacterial count was found in the CoCrMo + Zr surface disc (6.6 x 104 CFU/mL ± 4.6 x 104 SD) followed by the CoCrMo surface (1.1 x 105 CFU/mL ± 1.9 x 105 SD), the titanium surface (1.36 x 105 CFU/mL ± 1.8 x 105 SD), the rough stainless steel surface (2.65 x 105 CFU/mL ± 3.8 x 105 SD), and the rough titanium surface (2.1 x 105 CFU/mL ± 3.0 x 105 SD). The mean CFU count was lower for CoCrMo + Zr discs compared with the rough stainless steel surface (mean difference: 2.0 x 105, p = 0.021), the rough titanium alloy surface (mean difference: 1.4 x 105, p = 0.002), and the smooth titanium surface (mean difference: 7.0 x 104, p = 0.016). The results of biofilm formation quantification show that the mean covered area of the surface of the CoCrMo + Zr discs was 19% (± 16 SD), which was lower than CoCrMo surfaces (35% ± 23 SD), titanium alloy surface (46% ± 20 SD), rough titanium alloy surface (66% ± 23 SD), and rough stainless steel surface (58% ± 18 SD).
These results demonstrate that a multilayer, ceramic-covered, CoCrMo surface with a 2.5-µm zirconium nitride top coat showed less S. epidermidis biofilm formation compared with other surface materials used for orthopaedic implants.
CoCrMo with a 2.5-µm zirconium nitride top coat seems to be a promising surface modification technology able to reduce bacterial attachment on the surface of an implant and, hence, may further prevent implant infection with S. epidermidis biofilm formation.
M. Pilz, K. Staats, R. Windhager, J. Holinka, Department for Orthopedic and Traumatology, Medical University of Vienna, Waehringer Guertel, Vienna, Austria
S. Tobudic, Department of Internal Medicine I, Division for Infectious Diseases and Tropical Medicine, Medical University of Vienna, Vienna, Austria
O. Assadian, E. Presterl, Department for Hospital Epidemiology and Infection Control, Medical University of Vienna, Vienna, Austria
O. Assadian, Department for Hospital Epidemiology and Infection Control, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria, email: firstname.lastname@example.org
The institution of one or more of the authors (EP) has received, during the study period, funding from CuraSolutions (Wiener Neustadt, Austria), outside this submitted work. One of the authors certifies that he (RW), or a member of his immediate family, has received or may receive payments or benefits, during the study period, an amount of less than USD 10,000 from DePuy Synthes/Johnson & Johnson Medical Products GmbH (Vienna, Austria), less than USD 10,000 from Pfizer Corporation Austria GmbH (Vienna, Austria), less than USD 10,000 from Stryker Austria GmbH (Vienna, Austria), less than USD 10,000 from Takeda Pharmaceutical Company Ltd (Tokyo, Japan), and less than USD 10,000 from Zimmer Biomet Austria GmbH (Vienna, Austria) for consulting. This work was performed using the routine research fund of the Department for Orthopedic and Traumatology, Medical University of Vienna, Austria (RW).
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Received April 18, 2018
Accepted October 19, 2018